Trust & methodology
Data Sources
Every figure in a KalkWise calculator traces to an authoritative source. This page lists what we use, where it comes from, and how often it is reviewed. Last updated July 2026.
Federal income tax
Annually (new tax year)Tax brackets, standard deductions, filing-status thresholds
Source: Internal Revenue Service (IRS)
FICA / payroll taxes
AnnuallySocial Security rate (6.2%) and wage base, Medicare rate (1.45%) and additional Medicare surtax
Retirement contribution limits
Annually401(k), IRA, Roth IRA, HSA contribution limits and catch-up amounts; RMD tables
Source: IRS (notices & publications)
State income tax
Annually + after legislative changesState brackets and flat rates used in paycheck, income tax, and self-employment calculators
State sales tax
AnnuallyCombined state + average local sales tax rates for all 50 states
Social Security benefits
As rules changeClaiming-age adjustment factors, full retirement age rules
Inflation
Reviewed annuallyHistorical CPI used for inflation and real-return calculations
Mortgage & loan math
No periodic review neededAmortization, payment, and payoff formulas
Source: Standard actuarial formulas (no external data needed)
FHA / loan program rules
As programs changeFHA MIP rates, down-payment minimums
Source: U.S. Department of Housing and Urban Development (HUD)
How updates work
All tax constants live in a single shared data file, so a rate is never updated in one calculator and forgotten in another. 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 and every affected calculator picks up the new figures in the same release. Mid-year legislative changes — like the 2025 One Big Beautiful Bill Act — are applied as soon as the IRS or Treasury publishes implementing guidance, and the affected pages' "last updated" dates change only when their numbers actually change, so the date you see is meaningful.
Every calculator's result 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.