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 federal income-tax wages but not FICA. Pennsylvania keeps these contributions in state income-tax wages. 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-specific income and premium bases are applied separately. For example, Rhode Island TDI excludes supported retirement and health deductions, while Minnesota and Massachusetts Paid Leave include employee salary deferrals. 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. Pennsylvania requires local EIT/wage-tax and LST confirmation; Ohio requires municipal and school-district amounts, and West Virginia requires any city fee. All newly added state forms also require confirmation of other payroll charges. Maryland combines state and county tax in one table result and needs a confirmed county table category. 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.

Minnesota, Maine and Massachusetts require confirmed employee Paid Leave shares and prior covered wages. Rhode Island includes TDI/TCI, Pennsylvania employee unemployment, and Hawaii a payroll-confirmed TDI amount. Never enter the same deduction twice. State pages disclose date gates and source-table limitations.

• Washington: formula, worked example and sources
• Virginia: formula, worked example and sources
• Alabama: formula, worked example and sources
• New Hampshire: formula, worked example and sources
• Kentucky: formula, worked example and sources
• Indiana: formula, worked example and sources
• Louisiana: formula, worked example and sources
• Iowa: formula, worked example and sources
• Idaho: formula, worked example and sources
• Colorado: formula, worked example and sources
• Illinois: formula, worked example and sources
• Michigan: formula, worked example and sources
• Texas: formula, worked example and sources
• Florida: formula, worked example and sources
• Tennessee: formula, worked example and sources
• Wyoming: formula, worked example and sources
• North Carolina: formula, worked example and sources
• Pennsylvania: formula, worked example and sources
• Minnesota: formula, worked example and sources
• Rhode Island: formula, worked example and sources
• Georgia: formula, worked example and sources
• Hawaii: formula, worked example and sources
• Maryland: formula, worked example and sources
• Oklahoma: formula, worked example and sources
• South Carolina: formula, worked example and sources
• Nebraska: formula, worked example and sources
• Utah: formula, worked example and sources
• Maine: formula, worked example and sources
• Montana: formula, worked example and sources
• Ohio: formula, worked example and sources
• Massachusetts: formula, worked example and sources
• Kansas: formula, worked example and sources
• West Virginia: formula, worked example and sources

Bonus and overtime

The national bonus tool isolates federal incremental withholding and FICA. Linked state bonus tools add only their stated supported state method and entered bonus deductions; Unconfirmed local or program charges keep an estimate partial. Colorado bonus income withholding is manually supplied by payroll; its federal and standard FAMLI components are calculated. Flat-rate eligibility must be confirmed. The national aggregate method assumes one bonus with regular wages in the same paycheck. State bonus pages require regular wages paid before a separate bonus in the same payroll period, and use those wages for the federal aggregate calculation. All bonus tools use the standard W-4 settings shown in the form.

The national overtime tool illustrates the federal 40-hour baseline. Six state tools add their documented daily, weekly and, in California, seventh-day and double-time rules for a restricted ordinary-worker schedule. They do not determine eligibility. Optional extra-pay comparisons calculate federal deductions and require entered incremental state/local/benefit charges; they are not full payroll calculations. 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.

Income percentiles and self-employment

Income percentiles use weighted Census 2025 CPS ASEC tables describing 2024 pre-tax money income. Individual and household populations differ. Interpolated points inside finite income bins are approximations; open tails return ranges only. These are not confidence intervals.

The 1099 estimator uses 2026 annual federal tax schedules, not payroll withholding tables. It separates self-employment tax, ordinary income tax and Additional Medicare under a limited standard-deduction profile. QBI is excluded unless the user selects the supported bounded option. State/local taxes, AMT and other stated items remain outside the model. Quarterly savings are not IRS payment installments.

Rounding, tests and limitations

Amounts generally round to cents; Idaho and North Carolina normal annualized withholding round to whole dollars. Iowa uses its published period deductions, and Indiana rounds exemption categories to cents. Oklahoma, Maine and West Virginia also use documented whole-dollar steps. Utah retains formula precision; Montana follows the literal round-up instruction despite conflicting examples. Maryland source anomalies in a few table ranges are blocked rather than silently corrected. 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.