Accounts eligible for rollover
Primary source
Verbatim text below is from the Electronic Code of Federal Regulations (eCFR), a public-domain U.S. government work. Always verify the current version with the eCFR before relying on it for any legal matter.
Full Text
(a) A participant who has an open TSP account and is entitled to receive (or receives) an eligible rollover distribution from an eligible employer plan within the meaning of section 402(c) of the Internal Revenue Code (26 U.S.C. 402(c)), or from a traditional IRA may roll over that distribution into his or her existing TSP account in accordance with § 1600.31.
(b) The only balances that the TSP record keeper will accept are balances that would otherwise be includible in gross income if the distribution were paid to the participant. The TSP record keeper will not accept any balances that have already been subjected to Federal income tax (after-tax monies) or balances from a uniformed services TSP account that will not be subject to Federal income tax (tax-exempt monies).
(c) Notwithstanding paragraph (b) of this section, the TSP record keeper will accept Roth funds that are transferred via direct rollover from an eligible employer plan that maintains a qualified Roth contribution program described in section 402A of the Internal Revenue Code.
(d) The TSP record keeper will accept a rollover only to the extent the rollover is permitted by the Internal Revenue Code.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.