If the "thrift savings plan" is not an IRA or 401K plan, then the money was put in after taxes were paid on that income. Therefore you won't get a 1099 for money pulled out of that account. E.G. I put money into a 401K plan, part of which was before taxes up to the government limit. I put in additional money beyond the limit, which was taken from after taxed money. So when the 1099 came on money pulled out of the fund, it showed how much was taxable (the money taken pretax) and how much was left not taxable -- the money pulled out beyond that was from the part taken from money already taxed. My taxes went up suddenly after being retired a few years because I had been pulling out the "after tax" money - and was not charged income tax on it - just the Social Security. Then when that post-tax money ran out, I dipped into the pretax (ira) money, and was taxed on all of that..