What Is a 401(k) True-Up, and Why You Need to Know.

Your employer says it will match 50% of the first 6% of pay you put into your 401(k). That sounds like a promise about the whole year: contribute 6% of your salary, collect a match worth 3% of your salary. But for a great many plans it isn't a yearly promise at all — it's a per-paycheck one. And that small distinction can quietly cost a saver thousands of dollars a year in free money.

The fix for it has an unglamorous name: a true-up. Most people have never heard of it, it's buried in the plan documents, and whether your employer offers one can change your retirement balance by hundreds of thousands of dollars over a career. Here's what it is, how you can lose match without it, and how to find out where you stand.

The Definition

What a true-up actually is.

A true-up is an extra employer contribution, made after the end of the year, that makes up any matching money you missed because of when you contributed — so you end up with the full match you would have earned by spreading your contributions evenly across the year. In the words of a payroll-industry glossary, it is "an additional, end-of-year contribution employers add to an employee's 401(k) plan to make up the difference between the matching funds an employee received and the amount they were supposed to receive" (Paylocity). With a true-up, as the Society for Human Resource Management puts it, "the employer makes good on the full promise of the employer's match, regardless of when employees reached the annual contribution limit" (SHRM).

Which raises the obvious question: how could you miss match in the first place, if you contributed enough to earn it?

The Mechanics

How the match is really calculated.

The answer is that most plans fund the match one paycheck at a time. Each pay period, the plan looks at what you contributed that period and matches the first 6% of that paycheck's pay. To collect the full match, then, you need a qualifying contribution in every paycheck. Any paycheck where you contribute nothing earns no match — and that paycheck's match is gone for good.

Consider a worker earning $180,000, paid every two weeks (26 paychecks). Six percent of pay is about $415 per paycheck, so the match — 50% of that — is about $208 per paycheck, or $5,400 for the full year. That $5,400 is the prize. Whether you collect all of it depends entirely on your contribution pattern.

Two everyday habits trigger this. The first is front-loading — contributing heavily early to reach the IRS annual limit ($24,500 in 2026) well before December. Once you hit the limit, your contributions stop, and so does the match, for the rest of the year. A saver who fills the limit over the first six months earns match on only 13 of 26 paychecks — about $2,700 instead of $5,400. Someone who maxes out in the first couple of months does far worse.

The second habit is irregular contributions — for example, dumping a big slice of a bonus into the plan. As SHRM notes, per-paycheck matching "eliminate[s] the ability for employees to contribute unevenly throughout the year," including "making large contributions out of bonus payments," without losing part of the match. The plan doesn't punish you on purpose; it simply never sees a contribution in the empty paychecks, so it never adds a match for them.

How Common Is This?

More plans than you'd think leave you exposed.

This isn't a rare edge case. According to the Plan Sponsor Council of America's 68th Annual Survey of 401(k) plans (covering 2024), most plans that match fund it during the year rather than in a single year-end lump. Among those plans, about 38% add a year-end true-up, roughly 25% simply keep matching every payday, and about 34% stop the match early and offer no true-up at all. In other words, roughly a third of these savers are in plans where front-loading or uneven contributions can cost them match they'll never get back.

The Five-Minute Check

Find out which kind of plan you have.

You cannot tell from the outside whether your plan trues up — you have to ask. It's worth a short email to your HR or benefits team, or a look at your Summary Plan Description, to answer two questions:

If Your Plan Doesn't True Up

The fix is free, and the math is worth it.

If you learn that your plan matches per paycheck and does not true up, the remedy costs you nothing: contribute the same total, but spread it evenly so that every paycheck carries at least enough to earn the full match. Same money out of your pocket, same annual total into the plan — but now you collect the whole $5,400 instead of a fraction.

Over a career, the difference compounds into real wealth. The chart below runs our $180,000 saver for 20 years against the actual returns of the U.S. stock market, changing only the contribution pattern.

One caution: don't overcorrect. The goal isn't to contribute less — it's to make sure no paycheck is left empty. If you were front-loading to hit the annual limit, simply lower the per-paycheck percentage so the contributions stretch across all 26 paychecks and still add up to the same total. And if your plan does true up, none of this applies — front-load to your heart's content and enjoy the extra time in the market.

The Takeaway

One question, a very large answer.

A true-up is the safety net that makes contribution timing harmless. With one, your match is whole no matter when you contribute. Without one, contributing early or unevenly can silently forfeit thousands of dollars a year, and hundreds of thousands over a career. You can't change whether your plan has a true-up, but you can find out in five minutes — and if it doesn't, you can protect your full match for free by spreading your contributions across every paycheck.