Why Is My Paycheck Lower Than Expected?

A smaller-than-expected paycheck almost always traces to one changed line, not to the whole check being wrong. The usual causes: a benefits or retirement deduction changed (open-enrollment premiums reset, or a 401(k) auto-escalation stepped up your rate); the calendar year rolled over, which resets the Social Security wage base and the federal withholding tables; you crossed a mid-year threshold such as the 0.9% Additional Medicare Tax above $200,000; your W-4 changed; a bonus or commission in the same period was withheld under supplemental-wage rules; or your hours, overtime, or shift differential simply differed. Put this stub next to the previous one and compare the same lines in order — the gap is nearly always a single line with a knowable cause.

The frustrating part of a short paycheck is not the money, it is not knowing which of a dozen moving parts moved. Below is the full list, roughly ordered by how often each is the culprit, followed by a diagnostic table and the one case that is a genuine payroll error worth raising.

1. A Deduction Changed (Most Common)

Deductions change more often than taxes do, and usually without an announcement you registered at the time.

• Benefits open enrollment. Medical, dental, and vision premiums typically reset at the plan year and typically go up. Because most are pre-tax through a Section 125 plan, a premium increase lowers take-home by less than its face amount — but it still lowers it. See which deductions are pre-tax.
• 401(k) auto-escalation. Many plans automatically raise your contribution rate by a percentage point on a set date each year unless you opt out. Nothing arrives in the mail; the rate on your stub just goes up.
• A new HSA or FSA election. Annual elections are divided across the year’s paychecks, so a higher election means a bigger per-check deduction. See HSA vs FSA.
• A dependent added to coverage. Moving from employee-only to employee-plus-family is often the single largest deduction change a person ever sees.
• A garnishment order started. Court-ordered, taken from after-tax pay, and subject to federal limits on how much can be taken. See how much of your paycheck can be garnished.

2. The January Reset

If the drop happened in the first paycheck of a new year, it is almost certainly this, and several effects stack at once. The Social Security wage base restarts, so anyone who had earned past it the prior year — $184,500 for 2026 — and stopped paying the 6.2% is paying it again from the first dollar. New IRS withholding tables take effect (IRS Publication 15-T). Benefit elections and 401(k) escalations start. January is the most predictable paycheck drop of the year and it is not an error.

3. You Crossed a Mid-Year Tax Threshold

Two thresholds change withholding partway through a year, in opposite directions.

• Additional Medicare Tax (paycheck goes down). Employers must withhold an extra 0.9% on wages above $200,000 in a calendar year, regardless of filing status, starting in the pay period you cross it (IRS Topic 751). Nothing about your salary changed; the rate on the wages above the line did.
• Social Security wage base (paycheck goes up). Once year-to-date wages pass $184,500 in 2026, the 6.2% Social Security tax stops for the rest of the year and take-home jumps. This is why some high earners see a raise in October that reverses in January.

4. Your W-4 Changed

A new W-4 — yours, or one filed during onboarding or a life-event update — changes withholding immediately. The usual culprits are checking the multiple-jobs box, removing a dependent, or entering extra withholding on line 4c. Each is intentional in the moment and easy to forget by the next paycheck. See when to update your W-4.

5. A Bonus or Other Supplemental Pay Was in the Same Period

Bonuses, commissions, and retroactive raises are supplemental wages and are withheld under their own rules — commonly a flat 22% federal rate, or blended with your regular wages under the aggregate method, which temporarily raises the withholding rate on the entire check. The result often looks like over-withholding, and frequently is; it settles at filing. See how supplemental wages are taxed.

6. Your Hours or Pay Periods Differed

The dull explanation is often the right one: fewer hours, less overtime, no shift differential, or unpaid time off. And on a biweekly schedule some years contain 27 paychecks rather than 26, with fixed deductions spread across only some of them — so the extra check carries a different deduction load. See the 27-paycheck year and how many paychecks are in a year.

Diagnostic Table

The One Case That Is a Real Error

Most differences are explainable and correct. The classic genuine mistake is Social Security tax still being withheld after your year-to-date wages passed the wage base — which happens most often after a mid-year job change, because each employer tracks the cap separately and neither knows about the other. If you had two employers in one year, you may have overpaid Social Security across both; that excess is recoverable when you file, but it is worth knowing rather than discovering by accident. Check the year-to-date Social Security figure against 6.2% of the wage base and see whether it stopped where it should have. For the full anatomy of the stub, see how to read a pay stub and FICA vs federal income tax.

Sources and Methodology

Federal withholding methods and tables: IRS Publication 15-T. Social Security and Medicare (FICA) rules, including the Additional Medicare Tax: IRS Topic 751. Employer tax guide and supplemental wage rules: IRS Publication 15 (Circular E). Cafeteria plans and pre-tax fringe benefits: IRS Publication 15-B. Limits on wage garnishment: U.S. Department of Labor, Title III of the Consumer Credit Protection Act. Figures use the 2026 Social Security wage base of $184,500 and the $200,000 Additional Medicare Tax threshold. General information, not tax advice; your plan documents and payroll records govern. Last updated July 26, 2026.