Every January, millions of Americans open their first paycheck and notice a slightly bigger deposit.
It's the IRS adjusting how much you're allowed to tuck into a 401(k), and most people never check whether their payroll software kept up.
For 2025, the employee contribution limit sits at $23,500.
Workers 50 and older can add another $7,500 in catch-up contributions, and those aged 60 through 63 get a special $11,250 catch-up figure thanks to a change tucked into federal retirement law.
Miss those numbers and you could be leaving tax-advantaged space on the table.
If you got a raise mid-year or your employer auto-enrolls you at a fixed percentage, your paycheck math may now push you over the limit by December.
Go over, and your plan administrator typically refunds the excess the following year.
That refund shows up as taxable income, and you may owe tax on earnings it generated.
Log into your plan's website, find the contribution percentage field, and do a little division.
Take the annual limit, divide by your remaining paychecks, and set your percentage to land just under it.
If you're paid twice a month with 24 checks left, that's roughly $979 per check to hit the max.
A common formula is 50 cents on the dollar up to 6% of salary.
That's free money, and it doesn't count against your $23,500 personal limit.
Total employer and employee contributions together cap out much higher, at $70,000 for 2025, so a generous match rarely causes a problem for ordinary earners.
Roth 401(k) contributions share the same $23,500 ceiling.
You can't double up by splitting between traditional and Roth accounts.
The limit is per person, not per account type, which trips up people who switch jobs mid-year and start contributing at two different employers.
If you maxed out at your old employer by June and then enroll in a new plan in September, your new payroll team has no idea what you already contributed.
You have to track it yourself and tell them to stop or limit deductions.
Otherwise you're staring at a refund and a surprise tax bill.
High earners should also know about a rule now in effect: if your prior-year wages topped $145,000, your catch-up contributions must go into a Roth account rather than pre-tax.
It's a quiet shift that changes the math for people in their late 50s and early 60s.
Once a year, check your contribution percentage, confirm the current IRS limit, and verify your year-to-date total in December.
Our take: the 401(k) limit is one of the few money rules you can fully control, and yet it's the one people review least.
Ten minutes in January beats a refund check and a tax headache in April.
Final Thoughts
Set a phone reminder, check the number, and let the payroll system do the rest.