Q. Are all TSP withdrawals subject to the 20-percent federal tax withholding, including full withdrawal by way of monthly payments? And is this done automatically when you set up your payout options with TSP or do you need to complete a form?
A. Not all TSP withdrawals are subject to mandatory withholding. See the table on Page 3 of the notice at https://www.tsp.gov/PDF/formspubs/tsp-536.pdf for the rules. Mandatory and default withholding happens automatically. Anything else, you’ll have to request.