According to Houston Financial Advisors, Richard J. Alphonso, JD, CPA/PFS, M.S.T. and C. Randy Scott, CPA, tax deductions for charitable donations are limited to a percentage of your adjusted gross income (AGI), which is also known as your "contribution base." This percentage is determined by the type of organization and the type of donation.

• Cash gifts.
The deduction for cash contributions can't exceed 50% of your AGI for the taxable year. For example, if your AGI is $200,000 and you donate $120,000 cash to charity this year, your deduction will be $100,000. Any amount not allowed in the current tax year may be carried forward for up to 5 years.
• Gifts of appreciated property.
As we mentioned above, gifts of capital gain property are usually deductible at their fair market value on the date of the contribution. So, 500 shares of publicly traded stock worth $36,000 would give you a charitable deduction of $36,000.
However, you must reduce your contribution deduction by its potential long-term capital gain if:
-you make the gift to certain private nonoperating (grantmaking) foundations (excluding gifts of appreciated publicly traded stock)
-the gift consists of personal property that will be put to a use that's unrelated to the organization 's function.