In practice, writing off 100 percent of your income through charitable donations is rare and only possible in limited circumstances. Your deduction is generally capped at a percentage of adjusted gross income that depends on the type of property given and the kind of organization receiving it. Cash gifts to most public charities often have the highest percentage limit, while gifts of appreciated property and contributions to certain private foundations have lower limits. Special legislation in some years has temporarily allowed higher caps for certain cash gifts, but those provisions do not normally apply to noncash property that requires an appraisal. If your contributions exceed the allowable percentage, the unused portion may often be carried forward to future years rather than deducted all at once.
