Trust & methodology

Data Sources

This page lists the sources we use, where they come from, and how often they are reviewed. Last updated October 2026.

Federal income tax

Annually (new tax year)

Tax brackets, standard deductions, filing-status thresholds

Source: Internal Revenue Service (IRS)

FICA / payroll taxes

Annually

Social Security rate (6.2%) and wage base, Medicare rate (1.45%) and additional Medicare surtax

Source: Social Security Administration (SSA) & IRS

Retirement contribution limits

Annually

401(k), IRA, Roth IRA, HSA contribution limits and catch-up amounts; RMD tables

Source: IRS (notices & publications)

State income tax

Annually + after legislative changes

State brackets and flat rates used in paycheck, income tax, and self-employment calculators

Source: State revenue departments; Tax Foundation summaries

State sales tax

Annually

Combined state + average local sales tax rates for all 50 states

Source: Tax Foundation (2025 mid-year rates)

Social Security benefits

As rules change

Claiming-age adjustment factors, full retirement age rules

Source: Social Security Administration (SSA)

Inflation

Reference only

Reference for the inflation rate you enter (no CPI history is stored)

Source: U.S. Bureau of Labor Statistics (CPI-U)

Mortgage & loan math

No periodic review needed

Amortization, payment, and payoff formulas

Source: Standard actuarial formulas (no external data needed)

FHA / loan program rules

As programs change

FHA MIP rates, down-payment minimums

Source: U.S. Department of Housing and Urban Development (HUD)

How updates work

Federal tax brackets, standard deductions and contribution limits live in a single shared data file. Each November, when the IRS publishes the next year's inflation adjustments (brackets, standard deductions, contribution limits, the Social Security wage base), we update that file once. Mid-year legislative changes — like the 2025 One Big Beautiful Bill Act — are applied as soon as the IRS or Treasury publishes implementing guidance.

Part of the calculator code is also covered by an automated verification suite: fixed input scenarios with hand-computed expected outputs that run before any change is published. When a law change alters an expected output, the test values are updated in the same release as the rate change — the suite fails loudly if they drift apart. As of October 2026, it covers 83 of our 164 calculation engines.

Found a figure that looks out of date? Tell us — confirmed data corrections are prioritized over all other work. See also our Editorial Policy and Disclaimer.