This is the accessible text file for GAO report number GAO-07-131R entitled 'Applying Agreed-Upon Procedures: Highway Trust Fund Excise Taxes' which was released on November 3, 2006. This text file was formatted by the U.S. Government Accountability Office (GAO) to be accessible to users with visual impairments, as part of a longer term project to improve GAO products' accessibility. Every attempt has been made to maintain the structural and data integrity of the original printed product. Accessibility features, such as text descriptions of tables, consecutively numbered footnotes placed at the end of the file, and the text of agency comment letters, are provided but may not exactly duplicate the presentation or format of the printed version. The portable document format (PDF) file is an exact electronic replica of the printed version. We welcome your feedback. Please E-mail your comments regarding the contents or accessibility features of this document to Webmaster@gao.gov. This is a work of the U.S. government and is not subject to copyright protection in the United States. It may be reproduced and distributed in its entirety without further permission from GAO. Because this work may contain copyrighted images or other material, permission from the copyright holder may be necessary if you wish to reproduce this material separately. November 3, 2006: The Honorable Todd J. Zinser: Acting Inspector General: Department of Transportation: Subject:Applying Agreed-Upon Procedures: Highway Trust Fund Excise Taxes: Dear Mr. Zinser: We have performed the procedures contained in the enclosure to this report, which we agreed to perform and with which you concurred, solely to assist your office in ascertaining whether the net excise tax revenue distributed to the Highway Trust Fund (HTF) for the fiscal year ended September 30, 2006, is supported by the underlying records. As agreed with your office, we evaluated fiscal year 2006 activity affecting distributions to the HTF. In performing the agreed-upon procedures, we conducted our work in accordance with U.S. generally accepted government auditing standards, which incorporate financial audit and attestation standards established by the American Institute of Certified Public Accountants. These standards also provide guidance for performing and reporting the results of agreed-upon procedures. The adequacy of the procedures to meet your objectives is your responsibility, and we make no representation in that respect. The procedures we agreed to perform were related to (1) detailed tests of transactions that represent the underlying basis of amounts distributed to the HTF, (2) Internal Revenue Service's (IRS) quarterly HTF certifications, (3) Department of the Treasury's Financial Management Service adjustments to the HTF during fiscal year 2006, (4) IRS's precertification[Footnote 1] of receipts for each quarter completed in fiscal year 2006, (5) certain procedures of the Department of the Treasury's Office of Tax Analysis' (OTA) process for estimating amounts to be distributed to the HTF for the fourth quarter of fiscal year 2006, and other procedures related to (6) the net amount of fiscal year 2006 excise taxes distributed to the HTF, (7) transactions that represent total IRS tax revenue receipts and refunds, and (8) key reconciliations of IRS records to Treasury records. The enclosure contains the agreed-upon procedures and our findings from performing each of the procedures. We were not engaged to perform, and did not perform, an audit, the objective of which would have been the expression of an opinion on the amount of net excise taxes distributed to the HTF. Accordingly, we do not express such an opinion. Had we performed additional procedures, other matters might have come to our attention that would have been reported to you.[Footnote 2] We completed the agreed-upon procedures on October 25, 2006. We provided a draft of this report to IRS and OTA officials for review and comment. IRS agreed with the results and findings presented in this report. OTA's review of the report only covered the procedures related to the estimation process for the quarter ended September 30, 2006. OTA agreed with the results and findings presented in this report relating to procedures performed on the estimation process for the quarter ended September 30, 2006. This report is intended solely for the use of the Office of Inspector General of the Department of Transportation and should not be used by those who have not agreed to the procedures and have not taken responsibility for the sufficiency of the procedures for their purpose. However, this report is a matter of public record, and its distribution is not limited. Copies are available to others upon request. This report is also available at no charge on GAO's Web site at http://www.gao.gov. If you have any questions, please call me at (202) 512- 3406. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. Sincerely yours, Signed by: Steven J. Sebastian: Director: Financial Management and Assurance: Enclosure: Highway Trust Fund Excise Tax Procedures and Results: I. Procedures on detailed transactions that represent the underlying basis of amounts distributed to the Highway Trust Fund (HTF) in fiscal year 2006: A. Nonstatistical selection of tax returns from the quarters ended June 30, 2005, and September 30, 2005[Footnote 3] 1. For each of the quarters ending June 30, 2005, and September 30, 2005, select the 30 largest excise tax returns containing excise taxes related primarily to the HTF and the Airport and Airway Trust Fund (AATF) on the basis of total tax liability amount[Footnote 4] from the Internal Revenue Service's (IRS) master file.[Footnote 5] Description of findings and results: We selected the 30 largest excise tax returns related primarily to the HTF and the AATF from each of the two quarters for testing. The selection was based on the total tax liability amount owed for each return from IRS's master file. The total tax liability amount related to the 30 returns from the quarter ended June 30, 2005, was approximately $9.7 billion, or 65 percent of the total excise tax liability amount of $15 billion for all excise tax types for the quarter. Of these 30 returns, 21 contained primarily HTF-related taxes and 9 contained primarily AATF taxes. The total tax liability amount related to the 30 returns from the quarter ended September 30, 2005, was approximately $9.8 billion, or 65 percent of the total excise tax liability amount of $15 billion for all excise tax types for the quarter. Of these 30 returns, 21 contained primarily HTF-related taxes and 9 contained primarily AATF taxes. 2. For each of the 42 returns related primarily to the HTF from the quarters ended June 30, 2005, and September 30, 2005, we performed the following procedures, which encompassed approximately $15 billion in prorated collections[Footnote 6] affecting fiscal year 2006 distributions to the HTF: (a) Trace the liability amount for abstracts[Footnote 7] 60 and 62 from the tax return to IRS's master file. Description of findings and results: The liability amount for abstracts 60 and 62 on the tax return agreed with the master file for 41 of the 42 returns. For one tax return for the quarter ended September 30, 2005, the taxpayer reported a credit for abstract 62, but the IRS did not have the supporting documentation to substantiate the credit. As a result, the prorated collection amount in the Collection Certification System may be overstated by $363,000 for abstract 62 and $107,000 for abstract 60. (b) Inspect the taxpayers' calculations on the tax return for the selected abstracts to determine whether they are mathematically correct. Description of findings and results: The taxpayers' calculations on all 42 returns were mathematically correct. (c) Calculate the prorated collection amount for the selected abstracts based on information from the master file and compare this amount to the amount from the Collection Certification System audit files.[Footnote 8] Description of findings and results: The independently calculated prorated collection amounts for the two selected abstracts agreed with the amounts in IRS's Collection Certification System for all 42 returns. B. Dollar unit sample (DUS) of transactions from the quarters ended December 31, 2005, and March 31, 2006: 1. Sampling: (a) Obtain excise tax collection data from the master file for the first two quarters of fiscal year 2006. Compare excise tax collection data from the master file with data from IRS's general ledger to determine if they materially agree.[Footnote 9] Compare total excise tax collections from the master file with total excise tax collections from the Collection Certification System audit files to determine if they materially agree. Description of findings and results: Excise tax collections for the first two quarters of fiscal year 2006 from the master file materially agreed with IRS's general ledger and with total excise tax collections from the Collection Certification System. (b) Select a random attribute sample of 78 excise tax assessments from the master file.[Footnote 10] Compare assessment and receipt information for each sample item from the master file to the assessment and receipt information in the Collection Certification System to determine if assessments and receipts from the master file are contained in the Collection Certification System. Description of findings and results: For 77 of the 78 sample items, assessments and receipts from the master file were contained in the Collection Certification System. For one sample item, the tax liability associated with the tax return was abated,[Footnote 11] however, the assessment amount of $18,000 for abstract 71 was not abated and, therefore, was incorrectly included in the Collection Certification System. (c) Sum the prorated collections for selected abstracts[Footnote 12] from the audit files and compare these amounts to amounts in the Report of Excise Tax Collection[Footnote 13] to determine if the Collection Certification System properly summarized the prorated collections. Description of findings and results: The Collection Certification System properly summarized the prorated collections for all of the selected abstracts. Prorated collections from the audit files for the selected abstracts agreed with the corresponding amounts in the Report of Excise Tax Collection. (d) Separate the total population of prorated collections from the audit files into the following distinct populations: (1) HTF, (2) AATF, and (3) other excise tax abstracts. Use DUS to select a sample of prorated excise tax collections from the HTF population using a confidence level of 80 percent, a test materiality of $379 million, and an expected aggregate error amount of $114 million. Description of findings and results: Use of DUS with a confidence level of 80 percent, a test materiality of $379 million, and an expected aggregate error amount of $114 million resulted in a sample of 94[Footnote 14] prorated collections for the HTF for the first two quarters of fiscal year 2006. (e) Select samples of prorated excise tax collections from the two non- HTF populations. Use DUS to select a sample of prorated excise tax collections from the AATF population using a confidence level of 80 percent, a test materiality of $103 million, and an expected aggregate error amount of $31 million. Select a random attribute sample of 45 items from the population of prorated tax collections related to all excise taxes other than the HTF and the AATF. Description of findings and results: Use of DUS with a confidence level of 80 percent, a test materiality of $103 million, and an expected aggregate error amount of $31 million resulted in a sample of 66[Footnote 15] prorated collections for the AATF for the first two quarters of fiscal year 2006. A random attribute sample of 45 items was selected from the population of prorated tax collections related to all excise taxes other than the HTF and the AATF.[Footnote 16] Detailed transactions: (a) For each prorated excise tax collection sampled from the HTF population: * Compare the assessment amount on the tax return for the sampled abstract with the amount recorded in IRS's master file. Description of findings and results: The assessment amount on the tax return agreed with the amount recorded in the master file for all of the sampled items. * Inspect the taxpayers' calculations on the tax returns for the related abstract to determine whether they are mathematically correct. Description of findings and results: The taxpayers' calculations were mathematically correct on the tax return for all of the sampled items. * Calculate the prorated collection amount based on information from the master file and compare this amount to the sample items selected from the Collection Certification System audit files.[Footnote 17] Description of findings and results: The independently calculated prorated collection, based on information from the master file, agreed with the amounts for all of the sampled items selected from the Collection Certification System audit files. (b) Inspect the tax returns and master file information for the two samples of prorated collections from the non-HTF populations to determine if they contain any HTF excise tax collections. Description of findings and results: The two samples of prorated collections from the non-HTF populations did not contain any HTF excise tax collections. (c) Evaluate the results of conducting steps (a) and (b). Description of findings and results: For the first 6 months of fiscal year 2006, the net most likely error is $0 with an upper error limit of $228 million at the 80-percent confidence level. II. Procedures on IRS's quarterly HTF receipt certifications: Perform the following procedures on IRS's HTF receipt certification for the quarters ended September 30, 2005, December 31, 2005, and March 31, 2006: A. Inspect the certification letters[Footnote 18] for authorizing signatures. Description of findings and results: The certification letters for all three quarters had authorizing signatures. B. Inspect the certification letters and supporting worksheets to determine if evidence exists that they were reviewed by the supervisor or another analyst. Description of findings and results: There was evidence that the supervisor or another analyst reviewed the certification letters and supporting worksheets for all three quarters. C. Calculate the totals on the certification letters to determine if they are mathematically correct. Description of findings and results: The totals on the certification letters for all three quarters were mathematically correct. D. Trace the certified amounts for diesel fuel tax (abstract 60) and gasoline tax (abstract 62)[Footnote 19] from the certification letters back to the Report of Excise Tax Collection[Footnote 20] and the Treasury 90 Report.[Footnote 21] Description of findings and results: The certified amounts for diesel fuel tax (abstract 60) and gasoline tax (abstract 62) from the certification letters agreed with the related Report of Excise Tax Collection and the Treasury 90 Report for the quarters ended September 30, 2005, and December 31, 2005. For the quarter ended March 31, 2006, the certified amounts for abstracts 60 and 62 from the certification letters agreed with the Report of Excise Tax Collection but not with the Treasury 90 Report. In deriving the certified amounts for abstracts 60 and 62 for that quarter, IRS deducted the incorrect amount of credits from the Treasury 90 Report. This resulted in a $15,398,992 understatement of the amount certified to the HTF for the quarter ended March 31, 2006. E. Compare the distribution rates used by IRS for diesel fuel tax (abstract 60) and gasoline tax (abstract 62) with the applicable laws.[Footnote 22] Description of findings and results: The distribution rates used by IRS for diesel fuel tax (abstract 60) and gasoline tax (abstract 62) agreed with the applicable laws in effect during all three quarters. F. Inspect the Report of Excise Tax Collection used in the certification to determine if it contains significant[Footnote 23] collections from prior quarters. Description of findings and results: The Report of Excise Tax Collection used in the certification for all three quarters did not contain significant collections from prior quarters. G. Trace heavy vehicle use tax amounts from the Highway Account certification letters to the master file.[Footnote 24] Description of findings and results: The heavy vehicle use tax amounts from the Highway Account certification letter agreed with the master file for all three quarters. III. Procedures on Financial Management Service adjustments: Perform the following steps on Financial Management Service (FMS) adjustments to HTF excise tax distributions for the quarters ended June 30, 2005, September 30, 2005, December 31, 2005, and March 31, 2006: A. Compare the FMS adjustments made to the HTF with original Office of Tax Analysis (OTA) estimates and IRS-certified amounts, and with the supporting schedules.[Footnote 25] Description of findings and results: The FMS adjustments made to the HTF accounts (Highway and Mass Transit) agreed with the original OTA estimates and IRS-certified amounts, and with the supporting schedules, for all four quarters. B. Calculate the differences between the OTA estimates and IRS- certified amounts to determine if the amounts agree with the differences computed by FMS. Description of findings and results: The independently calculated differences between the OTA estimates and the IRS-certified amounts for the Highway Account agreed with the differences computed by FMS for all four quarters. These amounts were[Footnote 26] * ($162,439,000) for the quarter ended June 30, 2005; * $388,440,000 for the quarter ended September 30, 2005; * ($321,139,000) for the quarter ended December 31, 2005; and: * $2,248,000 for the quarter ended March 31, 2006. The independently calculated differences between the OTA estimates and the IRS-certified amounts for the Mass Transit Account agreed with the differences computed by FMS for all four quarters. These amounts were: * ($64,407,000) for the quarter ended June 30, 2005; * ($20,809,000) for the quarter ended September 30, 2005; * ($74,917,000) for the quarter ended December 31, 2005; and: * ($10,322,000) for the quarter ended March 31, 2006. IV. Procedures on IRS's HTF precertification for the quarters ended September 30, 2005, December 31, 2005, March 31, 2006, and June 30, 2006[Footnote 27] A. Compare the precertified amount to the actual amount certified to the HTF for the quarters ended September 30, 2005, December 31, 2005, and March 31, 2006. If there is a significant variance,[Footnote 28] request from the IRS data on any large returns omitted from the precertification. Description of findings and results: There were no significant variances between the precertified amounts and the actual certified amounts for the quarters ended December 31, 2005, and March 31, 2006. For the quarter ended September 30, 2005, there was a significant variance of $755 million. $702 million of this was attributable to an error IRS made on the precertification related to the heavy vehicle use tax, which resulted in an understatement of the total HTF precertified amount. Because IRS's precertification is not an actual certification that results in any redistributions of excise taxes among the trust funds, this error did not have an effect on fiscal year 2006 distributions to the HTF. B. Perform the following procedures on IRS's HTF precertification for the quarter ended June 30, 2006: 1. Inspect the precertification letters and supporting worksheets to determine if evidence exists that they were reviewed by the supervisor or another analyst. Description of findings and results: There was evidence that the supervisor or another analyst reviewed the precertification letters and supporting worksheets. 2. Calculate the totals on the precertification letters to determine if they are mathematically correct. Description of findings and results: The totals on the precertification letters were mathematically correct. 3. Trace the amounts for diesel fuel tax (abstract 60) and gasoline tax (abstract 62)[Footnote 29] from the precertification letters back to the Report of Excise Tax Collection and the Treasury 90 Report. Description of findings and results: The precertified amounts for gasoline tax (abstract 62) from the precertification letters agreed with the related Report of Excise Tax Collection and Treasury 90 Report. The precertified amounts for diesel fuel tax (abstract 60) from the precertification letters agreed with the related Report of Excise Tax Collection but not with the Treasury 90 Report. In deriving the precertified amounts for abstract 60, the IRS deducted the incorrect amount of credits from the Treasury 90 Report. This resulted in an understatement of the precertified amount to the HTF for the quarter ended June 30, 2006, of $88,363,365. Because IRS's precertification is not an actual certification that results in any redistributions of excise taxes among the trust funds, this error did not have an effect on fiscal year 2006 distributions to the HTF. 4. Compare the distribution rates used by IRS for diesel fuel tax (abstract 60) and gasoline tax (abstract 62) with the applicable laws. Description of findings and results: The distribution rates used by IRS for diesel fuel tax (abstract 60) and gasoline tax (abstract 62) agreed with the applicable laws in effect during the quarter. 5. Inspect the Report of Excise Tax Collection used in the precertification to determine if it contains significant[Footnote 30] collections from prior quarters. Description of findings and results: The Report of Excise Tax Collection supporting the precertification did not contain significant collections from prior quarters. 6. Inspect the Collection Certification System information to determine whether IRS omitted any significant[Footnote 31] returns from the precertification. If so, report for the Highway Account and the Mass Transit Account (1) the average amount of HTF-related excise taxes from these taxpayers' returns that were included in IRS's certification from the four previous quarters and (2) the amount of HTF-related excise taxes from these taxpayers' returns that were included in IRS's certification for the quarter ended June 30, 2005. Description of findings and results: Our procedures did not identify any missing significant returns from the precertification. 7. Trace the heavy vehicle use tax amount from the Highway Account precertification letter to the master file. Description of findings and results: The heavy vehicle use tax amount from the Highway Account precertification letter agreed with the master file. V. Procedures performed on excise tax distributions to the HTF for the quarter ended September 30, 2006: A. Determine if OTA's process for identifying and incorporating the effect of new legislation on excise tax receipts into its trust fund estimates[Footnote 32] was in place during the quarter ended September 30, 2006. Description of findings and results: OTA's process for identifying and incorporating into its trust fund estimates the effect of new legislation on excise tax receipts was in place during the quarter ended September 30, 2006. OTA prepares a tax rate table[Footnote 33] to capture information relating to legislation that affects tax rates, tax basis, accounts, and deposit rules in effect during the quarter. B. Inspect the transfer forms and supporting schedules to determine if there is evidence of review. Description of findings and results: There was evidence that another OTA economist reviewed the transfer forms and supporting schedules for the semimonthly transfers affecting distributions to the HTF for the quarter ended September 30, 2006. C. Calculate the totals on the transfer forms to determine if they are mathematically correct. Description of findings and results: The totals on the transfer forms affecting distributions to the HTF for the quarter ended September 30, 2006, were mathematically correct. D. Trace the transfer amounts for diesel fuel tax (abstract 60), gasoline tax (abstract 62), and heavy vehicle use tax[Footnote 34] from the transfer forms through the supporting schedules and back to the related source documents.[Footnote 35] Description of findings and results: The transfer amounts for diesel fuel tax (abstract 60), gasoline tax (abstract 62), and heavy vehicle use tax from the transfer forms agreed with the supporting schedules and source documents for the semimonthly transfers affecting distributions to the HTF for the quarter ended September 30, 2006. VI. Other procedures: A. Using IRS's quarterly certifications, OTA's estimated distributions, and any adjustments, report excise taxes distributed to the HTF in fiscal year 2006. Description of findings and results: Based on a compilation of IRS's quarterly certifications, OTA's estimated distributions, and adjustments, the net amount of excise taxes distributed to the HTF in fiscal year 2006 was $38,754,503,680. B. Procedures performed as part of the fiscal year 2006 IRS financial statement audit: 1. From IRS's master files for the first 8 months of fiscal year 2006, use DUS to select statistical samples of (1) total tax revenue receipts and (2) refunds. For each sample item, compare the collection or refund amount, tax period, and tax class[Footnote 36] from source documentation with those recorded in IRS's master files. Description of findings and results: The receipt or refund amount, tax period, and tax class from source documents for 156 revenue receipts and 53 refund sample transactions were consistent with amounts recorded in IRS's master files. 2. Obtain selected IRS service center campuses' monthly Department of the Treasury (Treasury) FMS 224 reconciliations[Footnote 37] and determine whether IRS-reported revenue receipts and refunds were materially reconciled[Footnote 38] to Treasury FMS records. Description of findings and results: Tax revenue receipts and refunds reported by selected IRS service center campuses through the monthly Treasury FMS 224 reconciliation process materially reconcile to Treasury FMS records. 3. Compare tax revenue receipt balances by tax class, including excise taxes, and total refund balances recorded in IRS's general ledger with the master files and Treasury records to determine if they agree in all material respects. Description of findings and results: Tax receipt balances for all tax classes, including excise taxes, and total refund balances per IRS's general ledger materially agreed with IRS's master files and Treasury records. (196090): FOOTNOTES [1] To accommodate the Department of Transportation's accelerated reporting date for fiscal year 2006, IRS performed precertifications of excise tax collections. The data are for information purposes only and the precertification does not constitute an official certification. [2] In our report on the results of our audit of IRS's fiscal year 2005 financial statements, we noted a material weakness in IRS's financial reporting process (GAO, Financial Audit: IRS's Fiscal Years 2005 and 2004 Financial Statements, GAO-06-137, [Washington, D.C.: Nov. 10, 2005]). A component of this weakness includes IRS's inability to allocate excise tax collections to the appropriate trust funds at the time deposits are made. This condition affects the adequacy of the distributions of federal excise tax revenue to recipient trust funds and is a continuation of an issue that we have reported on in prior years. [3] Since certifications are not completed until 6 months after the end of the quarter, the certification and corresponding adjustment by the Department of the Treasury's (Treasury) Financial Management Service for the quarters ended June 30, 2005, and September 30, 2005, were completed in December 2005 and March 2006, respectively, and thus affected distributions to the HTF during fiscal year 2006. [4] Although the certifications are based on amounts collected, we used the tax liability amounts to identify the taxpayers paying the largest amounts of excise taxes. Our work shows that these taxpayers generally pay their excise taxes in full each quarter. [5] The master file is a detailed database containing taxpayer information. [6] IRS certifies to trust funds the amount of excise taxes collected. Because taxpayers have sometimes not fully paid their tax liability, IRS must allocate the amount of payments actually received among the different excise taxes reported on the taxpayer's return. IRS's Collection Certification System prorates a taxpayer's payments proportionately among all taxes reported as owed on the tax return. For example, if a corporation reports that it owes $4 million for gasoline tax, $2 million for diesel fuel tax, and $1 million for kerosene tax on its Form 720, Quarterly Federal Excise Tax Return, but has paid IRS only $3.5 million at the time IRS performs its certification, the program prorates the $3.5 million in the following manner: $2 million to gasoline tax, $1 million to diesel fuel tax, and $500,000 to kerosene tax. [7] The abstract numbers identify the tax type (e.g., gasoline and ticket tax) and are used as the basis for determining the distribution of the excise taxes to the various trust funds. Abstract numbers are preprinted on Form 720, Quarterly Federal Excise Tax Return, and are used by the taxpayer to report excise tax assessments. If the return was related to the HTF, we selected (1) diesel fuel tax (abstract 60) and (2) gasoline tax (abstract 62). If the return was related to the AATF, we selected (1) tax on transportation of persons by air (abstract 26), (2) tax on the use of international air travel facilities (abstract 27), and (3) tax on transportation of property by air (abstract 28). The tax amounts related to the selected abstracts for each trust fund are the largest tax amounts reported on the taxpayer's excise tax return and made up over 83 percent of the total amount certified to the HTF and over 90 percent of the total amount certified to the AATF for the quarters ended June 30, 2005, and September 30, 2005. [8] The Collection Certification System produces what IRS refers to as audit files. These audit files contain individual prorated collections by abstract and taxpayer identification number. The certified amounts to the trust funds are calculated by subtracting credits from prorated collections and then multiplying the difference by the applicable trust fund distribution rates. [9] For the purpose of this procedure, "material" is defined as 1 percent of the Form 720-related excise tax collections for the quarters ended December 31, 2005, and March 31, 2006. For fiscal year 2006, the materiality amount was $236 million for the two quarters combined. [10] For this sample, if one or no errors were found in testing the 78 items, we would be 90 percent confident that the error rate in the population would not exceed 5 percent. [11] Abatements are reductions in the amount of taxes owed and can occur for a variety of reasons, such as to correct errors made by IRS or taxpayers or to provide relief from interest and penalties. 26 U.S.C. ยง 6404. [12] The selected abstracts are (1) diesel fuel tax (abstract 60), (2) gasoline tax (abstract 62), (3) tax on transportation of persons by air (abstract 26), (4) tax on the use of international air travel facilities (abstract 27), (5) tax on transportation of property by air (abstract 28), and (6) tax on kerosene for use in commercial aviation (abstract 77). The tax amounts for the two HTF-related abstracts made up over 86 percent of the total amount certified to the HTF and the tax amounts for the four AATF-related abstracts made up over 99 percent of the total amount certified to the AATF for the quarters ended December 31, 2005, and March 31, 2006. [13] The Report of Excise Tax Collection contains prorated collections, classified by abstracts, that serve as the basis for IRS's quarterly trust fund certifications. [14] The planned sample size using DUS was 145 items. DUS selects dollars instead of specific transaction items by dividing the population by dollar intervals. The dollar interval for the HTF was $137 million. Accordingly, any item with a dollar value equal to or exceeding the sampling interval would be selected, whereas items with dollar values below the sampling interval might not be selected. For example, an item of $274 million would cover two dollar intervals, but represent one sample item. Due to large-dollar items covering more than one interval, the 94 unique sampled transactions selected represent 145 dollar intervals. [15] The planned sample size using DUS was 136 items. As explained in footnote 14, DUS selects dollars instead of specific transaction items by dividing the population by dollar intervals. The dollar interval for the AATF was $37 million. Because large-dollar items cover more than one interval, the 66 unique sampled transactions represent 136 dollar intervals. [16] For this sample, if no errors are found in the 45 items, we would be 90 percent confident that the error rate in the population would not exceed 5 percent. [17] The purpose of this procedure is to determine whether the Collection Certification System prorates correctly. This procedure is not intended to determine whether amounts provided to the system are correct. [18] IRS prepares two certification letters for the HTF each quarter: one for the Highway Account and the other for the Mass Transit Account. [19] The certified amounts for diesel fuel tax (abstract 60) and gasoline tax (abstract 62), along with the heavy vehicle use tax (traced separately), made up over 87 percent of the total amount certified to the HTF for the quarters ended September 30, 2005, December 31, 2005, and March 31, 2006. [20] IRS uses data from two of these reports, covering sequential processing intervals, for each quarterly certification. Collections are classified by abstract on the report when the related Form 720 tax return has been posted to IRS's master file during the processing interval covered by the report. The second of the two reports used may contain collections related to prior quarters that IRS certifies as part of the current quarter's collections because the related return was not posted to the master file until the processing interval covered by this report. [21] The Treasury 90 Report summarizes excise tax credit information and is produced quarterly by IRS submission processing campus systems. IRS has eight submission processing campuses that receive and process tax returns and payments. [22] IRS calculates certified collections to the Highway Account and the Mass Transit Account using the total prorated collection amount, tax rate, and distribution rates applicable to each account. [23] For this procedure, "significant" is defined as $175 million, which represents approximately 2 percent of the total amount certified to the HTF for the quarters ended September 30, 2005, December 31, 2005, and March 31, 2006. [24] These taxes, which go to HTF, are reported on Form 2290 and are not included in the Collection Certification System. [25] An FMS accountant compiles this schedule, called the "Subsidiary Quarterly Account of Estimates and Actual Related Excise Taxes Appropriated to Highway Trust Fund." This schedule computes the difference between IRS-certified amounts and the OTA estimate for excise taxes, individually and in total, that relate to the Highway Account. A similar schedule is prepared for the Mass Transit Account. The schedules, along with OTA transfer forms and IRS certifications, support the FMS adjustment. [26] A positive amount indicates that the FMS adjustment increased excise taxes distributed to the trust fund. A negative amount, shown in parentheses, indicates that the FMS adjustment decreased excise taxes distributed to the trust fund. [27] In order to accommodate the Department of Transportation's November 15 reporting date for fiscal year 2006, IRS performed precertifications of excise tax receipts. The data in the precertification are for information purposes only and do not represent an official certification for use in adjusting the excise tax distributions to the HTF. [28] Significant is defined as 5 percent of the actual certified amount for the quarter. [29] The certified amounts for diesel fuel tax (abstract 60) and gasoline tax (abstract 62) made up over 86 percent of the precertified amount to the HTF for the quarter ended June 30, 2006. [30] For this procedure, "significant" is defined as $175 million. This represents approximately 2 percent of the precertified total to the HTF. [31] For this procedure, "significant" is defined as tax returns with a total quarterly excise tax liability equal to or greater than $10 million during each of the prior four quarters. Tax returns related specifically to the HTF with liabilities equal to or greater than $10 million have, in the aggregate, historically accounted for over 91 percent of distributions certified to HTF. [32] OTA makes semimonthly estimates of excise tax collections for transfer to trust funds. There are five semimonthly estimates for the quarter ended September 30, 2006, which affect fiscal year 2006 distributions to the HTF. [33] OTA communicates this information to interested parties at Treasury and the Department of Transportation. IRS used the tax and distribution rates from this table in its subsequent certification of collections to trust funds. [34] The transfer amounts for diesel fuel tax (abstract 60), gasoline tax (abstract 62), and heavy vehicle use tax made up over 91 percent of the total amount transferred to the HTF for the fourth quarter of fiscal year 2006. [35] The source documents include the IRS report of excise taxes used to derive the percentages applied to reported receipts, the Daily Treasury Statement, the Monthly Treasury Statement, and the excise tax rate tables. [36] IRS assigns a tax class number to specific types of taxes. Excise taxes are tax class 4. [37] At the end of each month, each IRS campus provides Treasury its FMS 224 (Statement of Transactions) generated from IRS's general ledger, reporting receipts and refunds journalized during the month. Treasury reconciles the amounts on the FMS 224 with its records and provides IRS a Statement of Differences for any differences identified. [38] For the purpose of this procedure and procedure VI.B.3, we define "material" as $23 billion. This represents 1 percent of the estimated gross tax revenue receipts to be collected by IRS in fiscal year 2006. GAO's Mission: The Government Accountability Office, the investigative arm of Congress, exists to support Congress in meeting its constitutional responsibilities and to help improve the performance and accountability of the federal government for the American people. GAO examines the use of public funds; evaluates federal programs and policies; and provides analyses, recommendations, and other assistance to help Congress make informed oversight, policy, and funding decisions. GAO's commitment to good government is reflected in its core values of accountability, integrity, and reliability. Obtaining Copies of GAO Reports and Testimony: The fastest and easiest way to obtain copies of GAO documents at no cost is through the Internet. GAO's Web site ( www.gao.gov ) contains abstracts and full-text files of current reports and testimony and an expanding archive of older products. The Web site features a search engine to help you locate documents using key words and phrases. You can print these documents in their entirety, including charts and other graphics. Each day, GAO issues a list of newly released reports, testimony, and correspondence. GAO posts this list, known as "Today's Reports," on its Web site daily. The list contains links to the full-text document files. To have GAO e-mail this list to you every afternoon, go to www.gao.gov and select "Subscribe to e-mail alerts" under the "Order GAO Products" heading. Order by Mail or Phone: The first copy of each printed report is free. Additional copies are $2 each. A check or money order should be made out to the Superintendent of Documents. GAO also accepts VISA and Mastercard. Orders for 100 or more copies mailed to a single address are discounted 25 percent. Orders should be sent to: U.S. Government Accountability Office 441 G Street NW, Room LM Washington, D.C. 20548: To order by Phone: Voice: (202) 512-6000: TDD: (202) 512-2537: Fax: (202) 512-6061: To Report Fraud, Waste, and Abuse in Federal Programs: Contact: Web site: www.gao.gov/fraudnet/fraudnet.htm E-mail: fraudnet@gao.gov Automated answering system: (800) 424-5454 or (202) 512-7470: Public Affairs: Jeff Nelligan, managing director, NelliganJ@gao.gov (202) 512-4800 U.S. Government Accountability Office, 441 G Street NW, Room 7149 Washington, D.C. 20548: