METHOD & COVERAGE · AUGUST 31, 2026

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What we estimate

Regular resident W-2 payroll for the supported states, with a 2020-or-later W-4. Paycheck dates must be in 2026. Indiana county rates currently cover January–September; Idaho uses the revised July tables for dates on or after July 31. This is an estimate of withholding and entered deductions, not final annual tax liability or a payroll service.

Federal withholding and FICA

We use Worksheet 1A and the annual percentage tables in IRS Publication 15-T. The filing status, Step 2 checkbox and dollar amounts in Steps 3 and 4 adjust the withholding. Federal exemption does not turn off Social Security or Medicare.

Publication 15 supplies FICA and supplemental-wage rules. Prior taxable wages are with the same employer, before the current paycheck. A zero YTD value represents the first paycheck, not an annual average. The Social Security cap and additional Medicare threshold are applied to the current check.

Benefits and tax bases

Traditional 401(k) contributions reduce income-tax wages but not FICA. Supported qualified Section 125 accident/health insurance premiums reduce both. After-tax deductions do not reduce tax bases. Enter only amounts already qualified under your employer plan. We do not determine annual contribution limits, plan eligibility, FSA, HSA, dependent-care, life insurance or Roth treatment.

Sources: IRS 401(k) overview and Publication 15-B. State wage input follows supported qualified payroll exclusions; special state adjustments require professional review.

State forms and local charges

State controls are separate from the federal W-4. Indiana includes the selected January 1 resident county rate. Michigan city taxes and Kentucky, Alabama and Colorado local taxes require a confirmed per-paycheck amount. Washington also requires confirmation of any employee L&I charge. Until these amounts are confirmed, the result is labeled partial. A zero is a user-confirmed absence of a charge, not an automatic claim that none exists.

Standard WA Paid Leave and Colorado FAMLI employee premiums use gross wages and their wage caps. Employer-paid employee shares can be excluded. Approved WA Cares exemptions are supported. Private plans and special coverage exemptions are outside scope.

Bonus and overtime

Bonus calculations isolate federal incremental withholding and FICA; state taxes are excluded. Flat-rate eligibility must be confirmed. The aggregate method assumes one combined bonus with regular wages in the same paycheck and standard W-4 settings shown in the tool.

Overtime is a gross-pay illustration for one simple workweek under the federal 40-hour baseline. It does not determine eligibility or apply state daily rules. A qualified annual overtime deduction does not mean all overtime is exempt from payroll tax.

Rate conversion and holiday policies

The time-and-a-half tool multiplies an entered rate by 1.5 for the specified hours. Holiday pay separates worked-hour pay at a selected total multiplier from additional paid nonworked hours. Neither tool determines entitlement, stacks weekly overtime automatically or estimates tax. The same base pay is never added twice.

Rounding, tests and limitations

Amounts generally round to cents; Idaho normal annualized withholding rounds to whole dollars. Iowa uses its published period deductions, and Indiana rounds exemption categories to cents. Employer rounding can differ.

Automated tests cover hand-worked references, adjustments, date restrictions, caps and invalid inputs. Independent code review is not professional tax certification. Cross-state residence/work, multiple employers, nonresident aliens, stock pay, garnishments and tips are unsupported. Do not use the result to file taxes or run payroll.

Found an error? Email a hypothetical example; do not send tax returns or personal identifiers.