Your pay stub looks smaller than last month's, and nothing about your job changed. That happens more often than people think, and it is rarely a mistake. Here are the real reasons, in the order we see them most.
Social Security tax restarted in January
Social Security tax stops once you earn enough in a year — $184,500 for 2026. Once you pass that number, your paycheck grows, because that 6.2% stops coming out. In January, the clock resets and the tax starts again. That is the single biggest reason a January paycheck looks smaller than a December one.
A raise pushed part of your income into a higher bracket
Tax brackets only tax the money inside each band, not your whole paycheck. Still, a raise can push part of your income into a higher band for the first time. Your take-home pay usually still goes up, just by less than the raise itself.
Open enrollment changed your benefits
Health insurance premiums usually rise every year at open enrollment. A richer health plan, or a higher 401(k) or HSA contribution, takes more out before you ever see it. Check what changed on your benefits portal, not just your pay stub.
Your state or local tax rate moved
Some states adjust their tax brackets every year. A handful of cities and counties change local tax rates too, sometimes in the middle of the year. Run your numbers again below to see this year's real rate for your state.
A bonus or overtime check was withheld differently
The IRS treats a bonus as a separate wage type and withholds a flat 22% federal rate on it. That can feel like more tax than your normal paycheck takes, even though it usually evens out when you file. It is not a mistake, and it is not extra tax you owe.
Check your own numbers
Every one of these reasons is easy to test. Pick your state, enter last year's numbers, then enter this year's, and compare the two results side by side.
Choose your state and calculate →