Reject and resubmit, American Economic Journal: Economic Policy.Media:Under Review.Top donors in the U.S. often give through family foundations. How does tax policy affect contributions to and disbursements from foundations? I develop a model that distinguishes tax-subsidized contributions from socially valuable disbursements. I estimate how foundations respond to tax policy in the short-run and over time. I evaluate a reduction in the subsidy for contributions, and an increase in the minimum share of assets foundations must disburse annually. Both reforms cause foundations to draw down their assets, raising disbursements relative to contributions. The first raises substantial revenue with modest disbursement losses; the second increases disbursements with little revenue change.