Going over your Thrift Savings Plan (TSP) annual contribution limit creates an excess deferral. We keep every number current to the tax year, the same way we do across the TSP guides we publish. How much that costs you depends on whether you catch it before TSP's refund deadline each spring.
Service members on the Blended Retirement System (BRS) face one extra wrinkle. Requesting an excess refund raises the question of what happens to the government's matching money. Federal employees and troops holding a second job with its own 401(k) or 403(b) face a different wrinkle, since none of the payroll systems talk to each other.
What Counts as an Excess TSP Contribution
An excess TSP contribution happens the moment your own paycheck deferrals for the year cross the elective deferral limit set under Internal Revenue Code section 402(g). The number moves every year. For 2026, the Internal Revenue Service (IRS) set that limit at $24,500, up from $23,500 in 2025. TSP confirms the same number on its own 2026 contribution limits bulletin.
That $24,500 cap covers only what comes out of your own pay: traditional and Roth TSP contributions added together. It leaves out three things TSP adds on top of your own money:
- Agency or Service Automatic (1%) Contributions
- Agency or Service Matching Contributions, capped at 4% under BRS
- Traditional TSP contributions made from tax-exempt combat-zone pay
None of those three count against your personal $24,500 limit, though the matching piece has its own rules once an excess deferral triggers a refund, covered further down. See how BRS matching is structured for the full mechanics of the 1% and match tiers.
How TSP Spillover Handles Catch-Up Contributions at 50 or Older
TSP automatically redirects any contribution past the elective deferral limit into your catch-up bucket once you turn 50, or you turn 50 later in that same calendar year. The spillover method replaced a separate catch-up election beginning with the first pay period of 2021, so a single contribution election now covers both buckets.
For 2026, the catch-up limit sits at $8,000 for anyone 50 or older. Anyone turning 60, 61, 62, or 63 that year gets $11,250 instead, under the enhanced catch-up the SECURE 2.0 Act added. Add either figure to the $24,500 base limit, and that is the true ceiling TSP will accept from your own pay before contributions stop.
Spillover also protects your match. Contributions never stop mid-year once you are catch-up eligible. Your BRS match keeps landing every pay period, instead of getting cut off the way it would for someone under 50 who hits the wall in October.
What Happens If You Are Under 50 and Go Over the Limit
TSP payroll systems cut off your own contributions the moment they hit the elective deferral limit if you have no catch-up eligibility. There is nowhere for the extra dollars to spill over, so the system simply stops taking money out of that pay period once you have contributed $24,500 for the year.
That cutoff usually means a true excess deferral cannot happen inside a single TSP account for someone under 50. The system will not process a contribution past the limit in the first place. One exception exists. A flat percentage election combined with a large bonus, drill-pay burst, or reenlistment payout can hit the $24,500 ceiling faster than planned. That leaves fewer pay periods for your match to land before the year runs out.
Setting your election as a flat dollar amount, instead of a percentage, spreads contributions evenly across all 26 pay periods and protects the full match. What we see readers get wrong most often is treating a percentage election as safe simply because the match never seems to stop, right up until a bonus pushes them past the limit in one pay period. The real risk under 50 almost never comes from TSP by itself. It comes from a second retirement plan outside TSP, covered next.
Spillover Eligibility Changes What an Excess Contribution Costs You
Age 50 is the line that decides whether an excess deferral is even possible inside TSP alone.
| Factor | 50 or Older (or Turning 50 That Year) | Under 50 |
|---|---|---|
| Catch-up eligible | Yes, automatically | No |
| What happens at $24,500 | Extra spills into catch-up, up to $8,000 more ($11,250 at ages 60 to 63) | TSP stops taking contributions |
| Can a true excess happen inside TSP alone | Rare, only past the combined cap | Almost never, unless combined with a second employer plan |
| BRS match risk | Continues all year | Can cut off early if contributions front-load |
The Real Tax Cost of an Uncorrected Excess Deferral
An excess deferral left in your TSP account past the correction deadline gets taxed twice. The IRS taxes it as income in the year you contributed it. Then it taxes the same dollars again in the year they finally come out of the account, whether that is next year or thirty years from now.
Run the math on a modest miss. Say you deferred $500 more than the 2026 limit and never filed a refund request. The IRS still counts that $500 on your 2026 tax return, exactly as if you had banked it in a checking account instead of TSP. Decades later, when you take a TSP withdrawal, the same $500 gets taxed again as ordinary income. The IRS rule on excess deferrals gives you no offsetting basis for the principal, so you pay tax on that $500 twice with no relief in between.
The earnings that excess deferral generated get taxed too, in whichever year they actually come out, on top of the double-taxed principal. Missing the correction window creates a second risk. It can also expose the distribution to the same rules that apply to any early TSP withdrawal. That includes the 10% early withdrawal penalty if you are under 59 and a half when it finally pays out.
The Deadline and Process for an Excess Refund
Fixing an excess deferral before it becomes a double-taxed dollar means requesting a refund, not just turning off future contributions. TSP opens its refund request window every January and uses Form TSP-44 for the request.
The TSP Service Office typically needs that form back by mid-March so it can pay the refund by the IRS's April 15 deadline. The exact cutoff date moves slightly each year, so confirm the current one on TSP's own contribution refunds page before you rely on it.
Requesting the refund returns your excess principal along with any earnings it produced. Those earnings are still taxable income in the year you receive them, even though the refunded principal itself avoids the double taxation an uncorrected excess would trigger.
The BRS Match Only Partly Survives a Refund
Not the whole match. Your service must remove the Agency or Service Matching Contributions tied to the excess, plus any earnings they produced, once you request a refund.
The Agency or Service Automatic (1%) Contribution works differently. It stays in your account regardless, because it is not tied to your own elective deferral and gets funded whether or not you contribute anything yourself.
An excess deferral refunded late in the year still costs you the match tied to those specific dollars, on top of the paperwork. Spreading contributions evenly across the year, so you never front-load past the limit, protects the full match. The refund process itself does not.
Military TSP Plus a Civilian 401(k) in the Same Year Is the Most Common Miss
The IRS applies the $24,500 elective deferral limit to you personally. It does not apply the limit to each plan separately, so a military TSP and a civilian employer's 401(k) or 403(b) in the same calendar year share one combined cap. That surprises reservists, National Guard members drilling around a civilian job, and veterans who separate mid-year and start a new 401(k) the same year they were still contributing to TSP.
Neither payroll system can see the other one. Your civilian 401(k) plan has no way to know what you put into TSP, and TSP has no way to know what you put into a 401(k) somewhere else. That means neither system stops you at the combined $24,500 limit the way TSP stops you on its own.
You have to track the combined total yourself and, if you go over, request the refund from one of the two plans before the same mid-March window covered above. Pick the plan where pulling the excess costs you less. That is usually the plan without an employer match tied to it, since BRS matching money already pulled from TSP cannot move to a civilian 401(k) instead.
How to Avoid an Excess TSP Contribution
A few habits catch most excess deferrals before they happen:
- Set your TSP election as a dollar amount, not a percentage, so a bonus or special pay cannot push you over the limit early.
- Check your year-to-date TSP contributions each quarter through your TSP account summary, not just at tax time.
- Add up every 401(k) or 403(b) contribution from any civilian job you held in the same calendar year, including one you left mid-year.
- Confirm your age-50 catch-up status is showing correctly if you turn 50 partway through the year, since spillover depends on TSP having your correct birth date on file.
- Mark mid-March on your calendar the year after any year you suspect you went over, in case you need to file Form TSP-44.
Most excess TSP contributions trace back to one of two things: a percentage election that outruns a bonus, or a second retirement plan payroll never told TSP about. Compare withdrawal options once your contributions are back on track at TSP withdrawal strategies, or check whether your fund lineup still fits your goals at the best funds for a TSP rollover. Check whether your own election is a flat percentage or a dollar amount before your next paycheck posts.