Paycheck
2026 paycheck withholding guide
Federal withholding, W-4, FICA, deductions, bonuses, state differences, a reproducible baseline, and source/testing methodology in one guide.
Read the paycheck guideLearning & evidence
Understand the tools - then inspect the evidence
Fewer, deeper guides plus public source provenance, reproducible calculator cases, and a factual maintenance history.
Three deep guides, plus the evidence behind the tools
PayCalc previously split many related topics into short standalone articles. We consolidated that material because a smaller number of comprehensive resources is more useful than overlapping pages. Start with a flagship guide, then inspect the underlying sources or test evidence.
Mortgage
Mortgage amortization & payoff guide
The fixed-payment formula, tested loan scenarios, extra principal, PMI, escrow costs, edge cases, and model boundaries.
Read the mortgage guideInvestment
Compound growth & rental-yield guide
Compounding conventions, scenario ranges, negative returns, incomplete periods, rental yield, and reproducible production cases.
Read the investment guideOriginal dataset
2026 payroll tax source directory
Browse the official source, verification date, tax model, and employee payroll programs represented for federal, all 50 states, and DC.
Open the source directoryReproducible evidence
Accuracy & testing center
See representative PayCalc browser cases and exact values the deployed site is expected to display.
Inspect the regression matrixOngoing maintenance
Update history
Review material changes to rules, source monitoring, regression testing, and content architecture. Dates represent real work.
Read the changelogWho creates this content?
PayCalc.org Editorial & Engineering maintains the calculators and supporting explanations. We prioritize primary government sources for payroll rules and publish model limitations rather than presenting estimates as professional advice. Automation and AI may assist with drafting, code, and testing; source selection, rule implementation, and expected calculation behavior are documented so they can be checked.