5 U.S.C. § 8440e — Members of the uniformed services

(a) Definitions. In this section: "basic pay" means basic pay under section 204 of title 37. A "full TSP member" is a member covered by subsection (e)(1), described below. "Member" has the meaning given in section 211 of title 37. "Secretary concerned" has the meaning given in section 101 of title 37.

(b) Who can contribute, and when they elect. Any member who qualifies to participate in the Thrift Savings Plan under section 211(b) of title 37 may contribute to the Thrift Savings Fund^*. Normally, a member elects to contribute the same way other participants do, under section 8432(b). But there's a special rule for members who were already serving as of the effective date tied to section 663 of the National Defense Authorization Act for Fiscal Year 2000: they could make their first election during the 60 days starting on that effective date, and that election would take effect on the first day of the next full pay period after those 60 days ended.

(c) Which rules apply. Except where this section says otherwise, the regular Thrift Savings Plan rules (this subchapter and subchapter VII) apply to contributing members, and for those purposes members are treated as "employees" under section 8401(11).

(d) Contribution limits.

• A member covered by section 211(a)(1) of title 37 can't contribute, out of basic pay, more than the maximum percentage set by section 8440f for that pay period.
• A member covered by section 211(a)(2) of title 37 can't contribute, out of the compensation received under section 206 of title 37, more than the maximum percentage set by section 8440f for that pay period.
• A member who is contributing out of basic pay or section 206 compensation may also transfer directly to the Fund any part of special or incentive pay received under chapter 5 of title 37.
• Nothing in this section or in section 211 of title 37 removes any dollar limit that already applies to the Thrift Savings Fund under the Internal Revenue Code.

(e) Modernized Retirement System^* — the government's own contributions.
(1) The Secretary concerned must make contributions to the Thrift Savings Fund, following section 8432's rules (except where this subsection changes them), for the benefit of a member who either (A) first joins a uniformed service^* on or after January 1, 2018, or (B) first joined before that date, had completed fewer than 12 years of service as of December 31, 2017, and elects — under section 1409(b)(4)(B) or 12729(f)(2) of title 10 — to receive these Thrift Savings Plan contributions in exchange for accepting reduced retired-pay multipliers under section 1409(b)(4)(A) or 12739(f)(1) of title 10.
(2) The maximum the Secretary concerned contributes for a "full TSP member" in any pay period is 5 percent of the member's basic pay for that period. This government^* contribution replaces — it is not added on top of — the contributions the government would otherwise make under section 8432(c).
(3) Timing of the government's contributions:

• Automatic contributions (the kind described in section 8432(c)(1)) start 60 days after the member first enters a uniformed service (for members covered by paragraph (1)(A)), or on the date of the member's election (for members covered by paragraph (1)(B)), and they continue until the member completes 26 years of service.
• Matching contributions (the kind described in section 8432(c)(2)) start 2 years and 1 day after the member first enters a uniformed service (for members covered by paragraph (1)(A)), or on the date of the member's election (for members covered by paragraph (1)(B)), and they also continue until the member completes 26 years of service.

(4) Section 8435, which protects spouses and former spouses, applies to a full TSP member the same way it applies to any other employee^* or Member covered by that section.