Roth vs Traditional IRA for federal employees: TSP, Roth TSP, and outside IRA
Federal employees on FERS have three income streams in retirement: the FERS basic pension, Social Security, and the Thrift Savings Plan (TSP). The pension and Social Security are both Traditional-like ordinary-income streams. The TSP can be Roth or Traditional or a mix. Adding a personal Roth IRA on top of the TSP creates a fourth income stream that is tax-free in retirement, balancing the otherwise Traditional-heavy retirement income picture.
The TSP contribution mechanics in 2026
The TSP follows the standard 401(k) elective deferral limits under IRC §402(g). For 2026 the limits are: $23,500 base elective deferral, $7,500 age-50 catch-up, $11,250 super catch-up for ages 60-63 (SECURE 2.0 §109). These apply across Roth TSP and Traditional TSP combined.
Federal employees on FERS also receive the agency automatic 1% contribution (paid even if you contribute zero) and agency matching contributions up to 4% on the first 5% of your elective deferral. So at a 5% elective deferral, you receive a 5% total agency contribution (1% auto + 4% match). At a 10% elective deferral, you still get 5% agency total. The match maxes at 5% of base salary.
The agency contributions always go to the Traditional bucket. This is a TSP plan-design choice, not a federal-statutory one. SECURE 2.0 §604 legalised Roth employer matches in 2023, but the TSP has not amended its plan documents to permit Roth agency contributions as of mid-2026. So a fed who directs 100% of elective deferral to Roth TSP still receives all agency money as Traditional. The Traditional bucket grows automatically from the agency side regardless of what you choose for your own contributions.
The TSP is unique among 401(k)-type plans in offering extremely low expense ratios on its core funds (the C, S, I, F, and G Funds, all under 5 basis points). The individual-stock-fund quality is comparable to Vanguard or Fidelity index funds at substantially lower cost. There is rarely a portfolio-quality reason to move money out of TSP after retirement; the cost advantage is structural.
The FERS pension as a Traditional-like income stream
The FERS basic annuity is a defined-benefit pension based on 1% of high-3 average salary per year of service (1.1% for retirees who claim at 62+ with 20+ years of service). A 30-year FERS employee retiring at 62 with high-3 salary of $130,000 receives approximately 33% of $130,000 = $42,900 per year. This pension is fully taxable as ordinary income at the federal level. It receives partial cost-of-living adjustments under the FERS rules (less than full CPI; typically about 1% less than CPI when CPI is above 3%).
Combined with Social Security at 62+ and any Traditional TSP withdrawals, a typical FERS retiree easily fills the 12% bracket and pushes into the 22% bracket on ordinary income alone. The Traditional-heavy income picture argues for tilting voluntary retirement contributions toward Roth, both inside TSP and outside in a personal Roth IRA.
A federal employee at $130K W-2 income with 5% TSP elective deferral plus 5% agency contribution + the FERS pension benefit accrual + Social Security is on track to a retirement income above $100K of ordinary income at age 62. The marginal tax bracket in retirement will be 22% federal (and potentially 24% if RMDs push it higher in your 70s). A Roth TSP contribution and a Roth IRA contribution today at the same 22% marginal cost lock in tax-free pools that do not push your retirement-bracket math even higher.
The Roth TSP option in detail
The Roth TSP was introduced in 2012. It allows federal employees to designate all or part of their elective deferral as Roth. The Roth portion is taxed in the year of contribution and grows tax-free, with qualified distributions tax-free in retirement.
Three things to note about Roth TSP that differ from a Roth IRA. First, Roth TSP withdrawals before age 59.5 follow the pro-rata rule between basis and earnings (just like a Roth 401(k)), not the contributions-first ordering of a Roth IRA. This means early withdrawals incur taxable earnings even if the principal portion is accessible. Second, Roth TSP balances were subject to RMDs through 2023, but SECURE 2.0 §325 eliminated the RMD requirement starting 2024. Roth TSP no longer has RMDs. Third, the 5-year qualification clock for Roth TSP runs from your first Roth TSP contribution to the TSP, not from your first Roth IRA contribution. These are separate 5-year clocks.
For someone planning to roll TSP to an IRA at retirement, the 5-year clocks become important. A Roth IRA opened decades earlier (with a long-running clock) lets you roll Roth TSP balances out and treat the funds under the longer Roth IRA clock. Opening a token $50 Roth IRA in your 20s, even if barely used, starts the 5-year clock running and is a no-cost insurance policy.
Adding a personal Roth IRA on top of TSP
The TSP limits and the personal IRA limits are independent. A federal employee can contribute $23,500 to the TSP (Roth or Traditional or mix) AND $7,000 to a personal Roth IRA in 2026, provided personal MAGI is below the Roth IRA phase-out ($150K single / $236K MFJ start).
For a fed earning $130K with the standard 5% TSP deferral ($6,500), agency match ($6,500), and a maxed personal Roth IRA ($7,000), total annual retirement contribution is $20,000 of voluntary saving plus $6,500 of agency contribution = $26,500. This is meaningful but does not max either the TSP elective deferral or the IRA fully. A fed who maxes both ($23,500 TSP + $7,000 Roth IRA + $6,500 agency) puts away $37,000 a year, comparable to a typical private-sector W-2 retirement saver.
A high-income fed (e.g. SES at $190K, or in a high cost-of-living area locality pay at $170K+) may face the Roth IRA income phase-out. The backdoor Roth IRA works for federal employees the same way it works for anyone else, with the same pro-rata trap. The TSP balance is NOT in the IRA pro-rata calculation, so a backdoor Roth IRA done by a fed with a $400K TSP balance is still clean. This is one of the structural advantages of TSP for high-income feds.
CSRS vs FERS and the differing retirement income mix
The Civil Service Retirement System (CSRS) closed to new hires in 1984; FERS replaced it. As of 2026, most active federal employees are FERS. The small remaining CSRS workforce is approaching or past retirement age.
CSRS provides a much larger defined-benefit pension (typically 56% of high-3 at 30 years vs FERS' 33% at 30 years) and does not include Social Security coverage for those years. A CSRS retiree's retirement income is dominated by the pension. The TSP is supplementary, not primary. The Roth-tilt argument is even stronger for CSRS retirees because the pension itself is so heavily Traditional-flavoured that adding Roth diversification has high marginal value.
FERS retirees have a smaller pension, full Social Security coverage, and a more substantial TSP. The TSP is roughly equal in importance to the pension. The Roth-tilt argument is still strong but less dramatic than for CSRS.
For both CSRS and FERS retirees, the personal Roth IRA on top of TSP is the cleanest way to add tax-free retirement income that does not push you into higher IRMAA or Social-Security-taxation thresholds.
FAQ
What is the TSP elective deferral limit in 2026?
$23,500 base. $7,500 age-50 catch-up. $11,250 super catch-up for ages 60-63 under SECURE 2.0 §109 (replaces, does not add to, the regular catch-up). These apply across Roth TSP and Traditional TSP combined.
Does the agency match go to Roth TSP?
No, always Traditional. SECURE 2.0 §604 legalised Roth employer matches in 2023 but TSP has not amended its plan to permit it as of mid-2026. Agency 1% auto and up to 4% matching always land in the Traditional bucket.
Can a federal employee contribute to a Roth IRA?
Yes, subject to standard income phase-outs ($150K-$165K single, $236K-$246K MFJ in 2026). For high-income feds, the backdoor Roth works cleanly because TSP balances are not in the IRA pro-rata calculation.
Should I roll TSP to an IRA at retirement?
Often no. TSP expense ratios are roughly 5 basis points, lower than most IRAs and even most low-cost index funds. Keeping balances in TSP retains the cost advantage. Reasons to roll: needing wider fund choice, consolidating accounts, or specific estate-planning structures that work better in an IRA.
Does Roth TSP have RMDs?
Not anymore. SECURE 2.0 §325 eliminated RMDs from designated Roth balances in 401(k)/403(b)/TSP plans starting 1 January 2024. Roth TSP now matches Roth IRA in having no RMDs during the original participant's lifetime.
What is the FERS pension and how does it interact with the Roth decision?
FERS basic annuity is 1% of high-3 average salary per year of service (1.1% if claimed at 62+ with 20+ years). It is fully taxable as ordinary income in retirement. The pension's Traditional-like character argues for tilting voluntary contributions toward Roth, both in TSP and in a personal Roth IRA.
Not financial, tax, or legal advice. Figures sourced from IRS Notice 2024-80 (2026 limits), TSP plan documents at tsp.gov, OPM FERS handbook, IRC §402(g) (elective deferral), SECURE 2.0 Act of 2022 §109 (super catch-up), §325 (Roth 401(k) RMD elimination), §604 (Roth employer match). Tax laws change. Consult a fiduciary financial advisor, CPA, or qualified retirement planner.