The Thrift Savings Plan is the federal government’s version of a 401(k), not an IRA. Asking whether the TSP is an IRA or a 401(k) is really asking which set of rules governs it, and the answer is the 401(k) rulebook: Congress created the TSP through the Federal Employees’ Retirement System Act of 1986 to give federal civilian employees and military members a defined contribution account with the same tax advantages private-sector workers get through employer-sponsored 401(k) plans. It runs on the same IRS contribution limits as a 401(k), it depends on your federal employment the way a 401(k) depends on your job, and it sits entirely outside the separate IRA system.
Why the TSP Is a 401(k), Not an IRA
The TSP and a private-sector 401(k) share the same basic architecture. Both are defined contribution plans, meaning your eventual balance depends on how much you and your employer put in, plus whatever those investments earn over time. Both use automatic payroll deductions, so the money never hits your bank account before it reaches the retirement plan. And both share the same IRS contribution limits under Section 402(g) of the Internal Revenue Code.
The plan is technically a government-sponsored trust managed by the Federal Retirement Thrift Investment Board, an independent agency in the executive branch. Board members are legally required to act solely in the interest of participants and beneficiaries. That fiduciary structure mirrors what the Department of Labor requires of private 401(k) plan administrators, though the legal authority comes from different statutes.
Like a Roth 401(k), the TSP offers a Roth option alongside its traditional pretax option, and you can split contributions between the two in any proportion. Traditional TSP contributions come out of your paycheck before federal income tax withholding and are taxed when you withdraw them. Roth TSP contributions come from after-tax dollars and, if you’re at least 59½ and five years have passed since January 1 of the year you made your first Roth TSP contribution, come out tax-free along with their earnings. Agency matching money always goes into the traditional balance regardless of how you designate your own contributions, so even an all-Roth contributor ends up with some pretax money in the account.
How the TSP Differs From an IRA
An IRA is a personal account you open yourself at a brokerage, bank, or credit union. Nobody has to employ you for you to open one, and you pick from thousands of investments. The TSP only exists because of your federal employment. You can’t walk into a bank and open a TSP account any more than you could walk in and open someone else’s 401(k).
The contribution limits run on completely separate tracks. For 2026, you can contribute up to $7,500 to an IRA (plus $1,100 in catch-up contributions if you’re 50 or older), while the TSP allows $24,500 in regular elective deferrals. Because the two limits are independent, you can max out both a TSP and an IRA in the same year. Income limits may restrict whether you can deduct a traditional IRA contribution or contribute to a Roth IRA at all, but the TSP has no income-based restrictions on who can participate.
Withdrawal mechanics also differ. The TSP carries the same 10% early withdrawal penalty as a 401(k) for taxable distributions taken before age 59½, along with a 401(k)-style exception that IRAs don’t offer: if you separate from federal service during or after the year you turn 55 (age 50 for public safety employees), you can withdraw without the penalty.
Where the TSP Beats a Typical 401(k)
Calling the TSP a 401(k) is accurate, but it undersells the plan on one point: cost. The TSP’s total expense ratios in 2025 ranged from 0.034% to 0.051% across its individual funds, lower than 99% of the roughly 170,000 investment funds cataloged on FactSet as of January 2026. A typical private-sector 401(k) charges somewhere between 0.50% and 1.00% in total fees. Over a 30-year career that gap compounds into real money, which is why many former federal employees leave their balances in the TSP after separating rather than rolling them to an IRA or a new employer’s 401(k).
The investment menu is deliberately narrow: five index funds covering government securities, bonds, large-cap U.S. stocks, small- and mid-cap U.S. stocks, and international stocks, plus Lifecycle (L) Funds that blend those five based on a target retirement date. A mutual fund window is available for participants who want access to thousands of additional funds, at a $37 annual administrative fee, a $95 annual maintenance fee, and $28.75 per trade on top of each fund’s own expense ratio.
The Federal Match
If you’re covered by FERS or the Blended Retirement System for uniformed services, your agency or branch puts money into your TSP on top of what you contribute. The match has two parts. First, an automatic 1% of basic pay every pay period regardless of whether you contribute anything yourself, yours after three years of service. Second, matching contributions on the first 5% of pay you contribute: dollar-for-dollar on the first 3%, and 50 cents on the dollar on the next 2%.
Contributing 5% of your basic pay gets you another 5% from your employer (the 1% automatic plus 4% in matching), an immediate 100% return on your own money. Contributing less than 5% leaves matching dollars unclaimed, which is the single most common mistake new federal employees make. Catch-up contributions do not receive any agency match.
TSP Loans, Another 401(k) Feature
Unlike an IRA, and like most 401(k) plans, the TSP lets you borrow from your own account while you’re still employed. A general purpose loan runs 1 to 5 years with a $50 processing fee and requires no documentation beyond the application. A residential loan, used only for buying or building a primary residence, runs 5 to 15 years with a $100 processing fee and requires supporting documentation within 30 days. The minimum loan is $1,000; the maximum is capped by a formula involving your own contributions, your vested balance, and any outstanding or recent loan balances, and never exceeds $50,000. You repay through payroll deductions, and the interest goes back into your own account.
2026 Contribution Limits
Because the TSP is a 401(k)-type plan, it shares the annual IRS elective deferral limits with 401(k)s. For 2026:
- Elective deferral limit: $24,500 for regular employee contributions.
- Standard catch-up (age 50 and older): an additional $8,000, for a total employee limit of $32,500.
- Enhanced catch-up (ages 60 through 63): an additional $11,250 instead of $8,000, for a total employee limit of $35,750. This higher catch-up was introduced by SECURE Act 2.0 and took effect in 2025.
- Annual additions limit: $72,000 total from all sources, including your contributions and agency automatic and matching contributions.
If you contribute to both a TSP and a private 401(k) in the same year because you changed jobs, your combined elective deferrals across both plans cannot exceed $24,500 (plus any applicable catch-up amount). The annual additions limit of $72,000 applies separately to each plan.
Rolling Money In and Out
The TSP accepts rollovers from traditional IRAs, 401(k)s, 403(b)s, and other eligible retirement plans. Current guidance uses either a rollover concierge service you reach by calling the ThriftLine or a self-service tool through My Account on tsp.gov; the older paper Form TSP-60 referenced in earlier guidance is no longer required. Once you leave federal service, you can roll your TSP balance into a private-sector 401(k), a traditional IRA, or a Roth IRA, though rolling traditional TSP money into a Roth IRA triggers income tax on the converted amount.
Who Can Participate
TSP eligibility is limited to people on the federal payroll: FERS employees (federal civilian workers generally hired on or after January 1, 1984), CSRS employees (federal civilian workers generally hired before that date who did not convert to FERS), and uniformed services members, including active duty military and Ready Reserve members covered by the Blended Retirement System. You must be in pay status to contribute. If you go into leave-without-pay status, contributions stop until you return. After you separate from federal service, you can no longer make new contributions, but your account stays open and invested until you withdraw the money or roll it elsewhere.