The assumptions should be as visible as the answer.
PlainSums publishes deterministic planning tools. This page records the calculation contract, public sources and known limitations behind the current release. It does not imply independent professional approval.
Which tax year these numbers are
Every rate, bracket, threshold and contribution limit on this site is the tax year 2026 figure. The federal parameters below are read directly from the code that does the arithmetic, so what you see here is what the calculators use — not a separately maintained copy that can fall out of step with them.
| Figure | 2026 | How it is applied |
|---|---|---|
| Standard deduction | $16,100 single / $32,200 married | Subtracted before the federal brackets are applied. |
| Social Security wage base | $184,500 | Employee rate 6.2%, charged once per year up to this amount and not at all above it. |
| Medicare rate | 1.45% | Employee rate on all wages. There is no wage cap. |
| Additional Medicare Tax threshold | $200,000 single / $250,000 married | 0.9% on wages above the threshold, employee only — there is no employer match. Employer withholding is triggered at $200,000 for everyone and reconciled on the return. |
| 401(k) elective-deferral limit | $24,500 | Standard employee limit; catch-up eligibility is not assumed. |
State schedules encode the same tax year. Where a state enacted a mid-cycle rate change for 2026, the change is reflected and noted on that state's page. Connecticut and New York do not tax high earners at their marginal rates alone — both claw back the value of their lower brackets — and those mechanisms are applied here from the state schedules listed below.
What the state pay tools calculate
The current state tools estimate annual federal income-tax liability, annual state income-tax liability and employee payroll taxes, then show that annual result across a selected number of periods. They do not reproduce an employer's payroll run.
True federal withholding uses pay-period wages and Form W-4 information under IRS Publication 15-T. State withholding can use different forms, percentages and wage bases. Until those mechanics and official fixtures are implemented, PlainSums labels the output as an annual take-home estimate and blocks filing schedules the data cannot support.
What the estimate leaves out
- Local, city and county income or occupational taxes.
- Work-state and residence-state reciprocity or multi-state allocation.
- Tax credits, dependants, itemized deductions and most Form W-4 adjustments.
- Income-based phase-outs of a state standard deduction or personal exemption. Every state deduction here is a fixed amount; where a state shrinks it as income rises (Connecticut, Maine, Maryland, Rhode Island, Utah and Wisconsin), that state's page says so.
- Married filing separately, which no state schedule in this data set covers.
- State payroll premiums and state-specific treatment of every benefit deduction.
- Year-to-date pay, prior withholding, bonuses and employer payroll rounding.
General calculator formulas
Loan tools use standard fixed-rate amortization. Saving and investing tools use compound-growth and annuity formulas with the timing shown beside each input. Scenario returns are steady mathematical assumptions, not forecasts or probabilities. Result statements show the components used by the calculation; anything not represented by an input should be treated as excluded.
Source register
- Internal Revenue Service: 2026 inflation adjustments and income-tax brackets
Federal annual-liability brackets and standard deductions.
- Internal Revenue Service: Publication 15-T (2026)
The payroll-withholding method PlainSums does not yet implement.
- Social Security Administration: 2026 contribution and benefit base
Social Security wage base and employee rate.
- Internal Revenue Service: Additional Medicare Tax
Liability thresholds and the additional 0.9% rate.
- Tax Foundation: 2026 state individual income-tax rates and brackets
Secondary compilation used as a starting reference; local taxes are excluded.
- Arizona State Legislature: Arizona Laws 2026, Chapter 140
Signed June 13, 2026; supersedes the earlier Arizona deduction snapshot.
- Plante Moran state and local tax advisor (April 2026): Supplemental budget with OBBBA conformity
Maine's 2026 IRC-conformity update; supersedes the earlier Maine deduction snapshot.
- Connecticut Department of Revenue Services: IP 2026(7), Is My Connecticut Withholding Correct?
Connecticut's 2026 rate table, 2% phase-out add-back and tax recapture tables.
- New York State Department of Taxation and Finance: Instructions for Form IT-2105 (2026)
New York's 2026 rate schedules and the tax computation worksheets that apply the supplemental tax above $107,650.
- Internal Revenue Service: 2026 401(k) and IRA contribution limits
Current employee deferral and IRA limits.
Validation and corrections
Automated tests cover core finance functions and release-specific regression cases, but do not constitute tax, payroll or financial review. Every one of the 51 jurisdictions is pinned to a hand-computed expected figure. Bracket boundaries, rates and deduction amounts have been checked against the 2026 schedules in the source register below, and Connecticut and New York additionally against their own state publications.
Two known gaps remain. Maine's standard deduction is disputed between published 2026 sources, so its figure is the least certain in the data set. And a secondary compilation, however carefully cross-checked, is not the statute — a state that changes its schedule after this release will be wrong here until it is updated. State estimates remain the largest residual data risk.
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