Your 401(k) Limit Is About to Hit $25,000. Most Savers Won't Notice the Difference.

Milliman's actuaries just ran the numbers, and the 401(k) employee deferral limit is on pace to hit $25,000 in 2027 — up from $24,500 this year and $23,500 in 2025. That's the fourth straight annual increase, and if your own contribution hasn't moved with it, the gap between what you're saving and what you could be saving just got wider again.

The IRS won't confirm the official 2027 number until early November, after September's inflation data locks the statutory formula in place. But the pattern isn't in question. The deferral limit has risen every year since 2021, tracking the same cost-of-living formula that also adjusts Social Security checks and tax brackets. What's easy to miss is that a fixed dollar contribution — the number you set once, years ago, and never touched — quietly shrinks in relative terms every time that cap moves and you don't move with it.

The $500-a-Year Habit Nobody Budgets For

Every autumn, the IRS runs the prior September's Consumer Price Index through a statutory formula, rounds to the nearest $500, and publishes the following year's limits. That mechanical process is why the 401(k) deferral cap moves in $500 increments instead of odd numbers, and why it rose to $24,500 for 2026 — up from $23,500 in 2025 — alongside a $7,500 IRA limit and an $8,000 catch-up contribution for savers 50 and older. Milliman's early 2027 projection has the deferral limit stepping up another $500 to $25,000, with the special "super catch-up" available to savers aged 60 to 63 rising from $11,250 to $11,750.

Two of those numbers are easy to conflate. The $24,500 figure is only the employee's own elective deferral — what comes out of your paycheck. The IRS also caps the combined total of your contributions plus your employer's match at $72,000 for 2026, projected to rise to $75,000 in 2027. Most savers never get near that combined ceiling; the number that actually governs your paycheck deduction is the smaller one, and it's the one climbing every year whether you notice or not.

None of that is trivia if you aren't already maxing out. It's a signal about how fast the target is moving under a contribution rate you set once and stopped thinking about. Scaling your contribution to track the cap isn't a market call or a lifestyle upgrade — it's a mechanical decision, the same one every year regardless of what the S&P did that month. Don't make it emotional. Make it automatic.

What Scaling Your Contribution Actually Buys You

Say you're 35, contributing a flat $20,000 a year to your 401(k), and you never raise that number again — a common pattern once the initial enrollment decision is made. Compare that to a saver who starts at the same $20,000 but adds roughly $500 more every year, tracking the pace the deferral cap has actually moved since 2023. Run both paths through the Compound Interest Calculator at a conservative 7% average annual return, and the gap isn't cosmetic.

At the end of 25 years, the flat contributor's account holds $1,264,964. The saver who scaled contributions up with the cap finishes at $1,538,165 — a difference of $273,201. The extra principal contributed over those 25 years comes to $150,000 (the sum of each year's $500 step), which means more than $123,000 of that gap didn't come from depositing more money. It came from depositing it earlier, so it had more years to compound.

The gap shows up at shorter horizons too, just smaller relative to the base. Over 10 years, scaling instead of staying flat is worth $27,260 more. Over 20 years, it's $149,968 more. The pattern holds at every stage: the earlier you start scaling, the more of the final gap comes from compounding rather than from the extra dollars themselves.

It's tempting to think you could skip the gradual scaling and just make it up with one large contribution close to retirement instead. The math above shows why that doesn't work as well: the value of a dollar in this calculation comes from how long it sits invested, not just how large the deposit is. A dollar added at age 35 has 25 years to compound at 7%; the same dollar added at age 55 has 10. Scaling early, even by a modest $500 a year, uses time as the multiplier. A late lump sum can only use size.

If you've been contributing the same dollar figure since your plan's open enrollment, the honest exercise is to plug your own number into the Compound Interest Calculator and add $500 for every year the cap has moved since — that's what you've actually been leaving on the table, not a hypothetical.

The Four-Year Window Before Retirement Nobody Maxes Out

The catch-up contribution matters more than its name suggests. Savers 50 and older get an extra $8,000 on top of the regular limit in 2026. But there's a second, narrower window: from age 60 through 63, the "super catch-up" created under SECURE 2.0 lets you contribute $11,250 in 2026 — $3,250 more than the standard catch-up — a gap Milliman projects widening to $3,750 in 2027, when the super catch-up is projected to reach $11,750.

That four-year window is short and it does not repeat. Miss it, and the extra catch-up room reverts to the standard $8,000 the year you turn 64. Add up the gap across all four years and it comes to roughly $13,000 in additional contribution room — before any market growth on top of it. For a saver who's behind in their late 50s, front-loading contributions specifically during ages 60 to 63, rather than spreading the same total across a longer stretch, is one of the few remaining levers that doesn't depend on the market cooperating. The Retirement Calculator is built for exactly this kind of late-career modeling: enter your current balance, your planned retirement age, and a four-year super-catch-up push, and see what it does to your number before you're actually 60 and out of runway to change course.

The IRS Makes This Official in November. You Don't Have to Wait.

You don't need the IRS's official announcement to act. The direction of the cap isn't in question, and the cost of leaving your own contribution flat while it climbs compounds every day you wait. Pick a number — even half of the $500 the cap has added each year — and change it in your plan portal this week, not after the 2027 figure becomes official in November.

If you've never modeled what a scaled contribution does to your actual retirement number, start with the Compound Interest Calculator using your real contribution and time horizon, then carry that number into the Retirement Calculator to see what it means for the age you can actually afford to stop working.