Every April 1st, final rules, which took effect over the past year, are incorporated into the compilation of the Code of Federal Regulations for Social Security.
For example, final rules which took effect April 1, 2006, through March 31, 2007, were incorporated into the April 1, 2007, compilation. Also, this version incorporated final rules published prior to April 1, 2007, which had effective dates beyond April 1, 2007.
If you want to look at regulations that are in effect currently, you must look at both the Code of Federal Regulations for Social Security, revised as of April 1, 2007, and the Final Rules -- April 1, 2007, to Date, which have been published in the Federal Register. This will give you a complete regulatory picture.