Limits on Deductions(p167)

The amount you can deduct for charitable contributions cannot be more than 50% of your adjusted gross income (AGI). Your deduction may be further limited to 30% or 20% of your AGI, depending on the type of property you give and the type of organization you give it to. If your total contributions for the year are 20% or less of your AGI, these limits do not apply to you. The limits are discussed in detail under Limits on Deductions in Publication 526.

A different limit applies to certain qualified conservation contributions. See Publication 526 for details.

You can carry over any contributions you cannot deduct in the current year because they exceed your adjusted-gross-income limits. You can deduct the excess in each of the next 5 years until it is used up, but not beyond that time. For more information, see Carryovers in Publication 526.