Start with your pay stub
Put your current stub next to a “normal” one and compare four things in order: gross pay, pre-tax deductions, taxes and after-tax deductions. The line that changed is your answer. Our guide to reading a pay stub explains each code.
1. Your first paycheck covers a partial period
If you started in the middle of a pay period, your first check pays only for the days or hours you actually worked. Salaried employees are often prorated by workdays. Many employers also pay in arrears: the check you get covers a period that ended a few days or a week earlier, so your first payday can come later and be smaller than a full check.
What to check: the pay period dates and hours on the stub.
2. Benefits deductions started
Health, dental and vision coverage often begins after a waiting period, so deductions can appear on your second or third check rather than the first. The same happens at open enrollment: a new plan year (often January) can bring new premiums.
What to check: lines such as MED, DEN, VIS, §125, HSA or FSA. Pre-tax premiums cut your take-home pay by less than their face value, because they also lower your taxes.
3. A new or higher 401(k) contribution
Some plans enroll new employees automatically, and some raise the percentage each year. A traditional 401(k) lowers federal income tax but not Social Security and Medicare. See the effect with the 401(k) paycheck calculator.
4. Your W-4 isn’t what you think
Federal income tax withholding follows the Form W-4 your employer has on file.
- No W-4 on file: your employer must withhold as if you were single with no adjustments. For a married person or a parent, that’s usually more than needed.
- Step 2 checkbox: if you checked the multiple-jobs box, the standard deduction and brackets are cut in half for this job, which raises withholding.
- Step 4(c) extra withholding: an amount entered here comes out of every check.
- Exempt status expired: a claim of exemption lasts only for one year. To stay exempt after 2026, you must give your employer a new W-4 by February 16, 2027; otherwise withholding starts again.
If anything looks off, file a new W-4 (see how to fill out a W-4).
5. A bonus or commission was withheld at a flat rate
Supplemental pay (bonuses, commissions, some back pay) can be withheld in two ways:
- Flat rate: 22% federal on the bonus, and 37% on supplemental pay above $1 million in the year.
- Aggregate method: the bonus is added to your regular pay for the period and withheld as if you earned that much every period. That can push the check into a higher withholding bracket.
Either way, Social Security, Medicare and state tax apply too, so a bonus check can look heavily taxed. The bonus tax calculator shows both methods. Over-withholding comes back when you file.
6. You moved, or now owe local tax
Moving to a new city or state can add a tax line. Examples include New York City (residents), Philadelphia, Detroit, many Ohio cities, Maryland counties and Pennsylvania’s local earned income tax. A move from a state like Texas or Florida to a state with income tax adds a state line. Working in a second state can add one too.
7. Social Security started again in January
Social Security is 6.2% of wages up to $184,500 per employer in 2026. If you earn more than that, Social Security drops off your stubs late in the year, and your checks get bigger. On January 1 the wage base resets and Social Security starts again, so your first checks of the new year are smaller, even with no change in pay.
The same happens with capped state programs. For example, New Jersey disability and family leave insurance stop at $171,100 of wages in 2026, and New York paid family leave stops at $411.91 for the year.
8. State payroll tax rates changed
Some state programs change their rates on January 1. In 2026:
- California SDI rose from 1.2% to 1.3%.
- Washington’s total paid leave premium rose from 0.92% to 1.13% of wages.
9. Additional Medicare kicked in
Once one employer has paid you more than $200,000 in the year, it withholds an extra 0.9% Medicare tax on every dollar above that. Checks after that point are a little smaller.
A word on three-paycheck months
If you’re paid biweekly, you get 26 checks in most years, and two months have three paydays. Those months don’t make any single check smaller: each check is figured the same way. What feels like a “lower” paycheck is often the gap between biweekly and semi-monthly pay. A $60,000 salary pays $2,307.69 gross every two weeks but $2,500 twice a month. Your 2026 pay schedule shows which months bring the third check.
Still can’t find it?
- Run your numbers in the paycheck calculator with the same W-4 and deductions, and compare each line with your stub.
- Check for after-tax deductions you didn’t expect, such as garnishments, union dues or a repayment of an advance.
- Ask payroll for an explanation. Employers can correct mistakes in later checks, and over-withheld federal income tax comes back when you file your return.