If you used a paycheck calculator last year and it still shows last year's numbers, it is not broken in the usual sense. It is out of date, because federal tax figures are set for one tax year at a time, and the new year's figures replace them on a fixed annual cycle.
This calculator uses the 2026 figures described here. A 2027 version will need the new Revenue Procedure figures before it can be trusted for 2027 pay.
Short answer first, then the calendar
Federal income tax brackets, the standard deduction, and the Social Security wage base are updated once a year, for the coming tax year. The IRS publishes the income tax figures in a Revenue Procedure in the autumn before the tax year starts. For 2026, that source is Revenue Procedure 2025-32, and it is the source named in the bracket and standard deduction guides on this site. Employers and payroll software then load the new figures, and withholding tables in IRS Publication 15-T are updated for the new year. A paycheck in January should therefore use the new year's figures, not the old year's, even if nothing else about the job changed.
- Autumn, before the tax year: IRS publishes the next year's brackets and standard deduction in a Revenue Procedure.
- Before January: payroll providers update withholding tables and wage base limits in their systems.
- January onwards: paychecks use the new year's figures, with the Social Security wage base restarting from zero for the year.
- During the year: figures normally stay fixed, unless Congress changes the law mid-year.
- Next autumn: the cycle repeats for the following tax year.
What changes every year, and what does not
| Figure | Usually updated yearly? |
|---|---|
| Income tax bracket thresholds | Yes, adjusted for inflation |
| Standard deduction | Yes, adjusted for inflation |
| Social Security wage base | Yes, indexed to wage growth, 184,500 dollars for 2026 |
| Social Security and Medicare rates | No, 6.2 percent and 1.45 percent are statutory rates |
| Additional Medicare thresholds | No, 200,000 dollars single, 250,000 dollars joint, and 125,000 dollars separate are fixed in law |
| W-4 form itself | Only when the IRS revises the form, not every year by default |
The distinction in that table explains two common surprises. A small inflation adjustment can move a bracket threshold by a few hundred dollars without changing any rate, so a salary near a threshold can sit in a different bracket in the new year. And a threshold that never moves, such as the additional Medicare threshold, can catch more earners over time as wages rise, even though no rate changed. This guide gives general information only, not a determination for an individual return.
The mid-year exceptions worth knowing
Mid-year changes are rare, but they are not impossible. Congress can change rates, deductions, or credits during a tax year, and a change of that kind can force payroll guidance to be updated after January. A second kind of mid-year change is personal, not systemic: a new W-4, a second job, a pay rise, or a change in pre-tax deductions changes withholding from the next pay period, even though the tables themselves did not move. A third kind is employer-specific: an employer can correct a payroll error, or switch payroll providers, and withholding can shift for a pay period for that reason alone.
State tables follow their own cycle and do not move with the federal cycle. A state can change its brackets, standard deduction, or flat rate on a different date, and a state paycheck page must be checked against that state's current figures, not against the federal update date.
How to tell whether a calculator is current
Check three things before trusting a result. First, does the page name the tax year it uses, and does it match the year of the paycheck you are estimating? Second, does it name a source for its figures, such as a Revenue Procedure number, rather than giving numbers with no source? Third, do its standard deduction and wage base match the current year's published figures, 16,100 dollars single and 184,500 dollars for 2026? If any of those checks fails, treat the result as a rough estimate for the wrong year, not as a precise figure for this year.
FAQs
Do I need a new W-4 every January?
No, not by default. A W-4 stays in effect until you file a new one. Review it when pay, jobs, marital status, dependents, or deductions change, rather than on a calendar date alone.
Why did my January paycheck change when my salary did not?
Because the new year's brackets, standard deduction, and Social Security wage base took effect in January. The wage base also restarted, so Social Security withholding resumed after it may have stopped late in the previous year.
Do state tables update at the same time?
Not necessarily. Each state sets its own schedule, so a state figure can change on a different date from the federal figures, and a state page should be checked separately.