What was your charitable donation? Was it capital gain? Does the following apply to you?
"A special 30% limit applies to contributions of capital gain property to 50% limit organizations. (For contributions of capital gain property to other organizations, see 20% Limit, later.) However, the special 30% limit doesn't apply when you choose to reduce the fair market value of the property by the amount that would have been long-term capital gain if you had sold the property. "
See IRS Pub 526, page 14 - https://www.irs.gov/pub/irs-pdf/p526.pdf
