Our Sources

IRS Revenue Procedure 2025-32

The official IRS inflation-adjustment publication for tax year 2026. Establishes all federal income tax bracket thresholds, the standard deduction, the AMT exemption, and dozens of other inflation-adjusted figures. This is the authoritative source for 2026 federal income tax parameters.

Key 2026 figures from this document:

• Single standard deduction: $16,100
• MFJ standard deduction: $32,200
• HOH standard deduction: $24,150
• 10% bracket top (single): $12,400
• 12% bracket top (single): $50,400
• 22% bracket top (single): $105,700
• 24% bracket top (single): $201,775

IRS Publication 15 (Circular E) — Employer's Tax Guide 2026

The IRS's official guide to federal income tax withholding. Contains the withholding tables employers use to determine per-paycheck federal income tax deductions. Used to cross-verify our per-paycheck calculations match IRS withholding expectations.

IRS Schedule SE and Publication 334

Governs self-employment tax calculation: the 15.3% rate (12.4% SS + 2.9% Medicare), the 92.35% net earnings multiplier, and the above-the-line deduction for half of SE tax. Source for our 1099 calculator mode.

IRS Publication 15-A — Employer's Supplemental Tax Guide

Source for the supplemental wage withholding rate (22% flat rate for bonuses and supplemental pay up to $1 million; 37% above $1 million) used in our bonus calculator.

IRS Notice 2013-45 / IRC Section 3101(b)(2)

Establishes the 0.9% Additional Medicare Tax on wages above $200,000 (single) or $250,000 (MFJ). This provision has been in effect since 2013 and confirmed as applicable for 2026. We apply this surcharge to all relevant calculations — a detail many calculators omit.

Social Security Administration — 2026 Cost-of-Living Adjustments

Official SSA source for the 2026 Social Security wage base ($184,500) and employee contribution rate (6.2%). Published annually each October for the following year.

IRS Notice 2025-70 — Retirement Plan Contribution Limits for 2026

Official source for 2026 retirement contribution limits: 401(k) / 403(b) elective deferral limit ($24,500), IRA contribution limit ($7,000), HSA individual limit ($4,300), HSA family limit ($8,550), and 50+ catch-up contribution amounts.

California Franchise Tax Board — 2026 Withholding Schedules

Source for California's progressive income tax brackets, the $5,202 standard deduction (single, 2026), and the 1.1% SDI rate. CA FTB Publication 1016 and the DE-4 withholding method.

New York State Department of Taxation and Finance — IT-2104

Source for New York State's progressive brackets ($8,000 single standard deduction, rates 4%–10.9%), and New York City income tax rates (3.078%–3.876%).

No State Income Tax — Constitutional and Statutory Provisions

Texas: Texas Constitution Article 8, §24 (no income tax without voter approval). Florida: Florida Constitution Article VII, §5 (banned since 1924). Nevada: Nevada Constitution Article 10, §1. Washington: No income tax on wages by longstanding court interpretation of WA Constitution Article VII, §1.

Illinois Department of Revenue — IL-700-T Withholding Tables

Source for Illinois's flat 4.95% income tax rate. Illinois Constitution Article IX, §3(a) requires a uniform tax rate — confirmed by voters rejecting a progressive tax amendment in November 2020.

NC Department of Revenue — 2026 Income Tax Withholding Tables

Source for North Carolina's 4.25% flat rate for 2026, reduced from 5.25% through legislated rate reductions under S.L. 2023-134.

Georgia Department of Revenue — 2026 Withholding Tax Tables

Source for Georgia's 5.39% flat rate for 2026. Georgia converted from progressive brackets to a flat system under HB 1437 (2022) with scheduled annual rate reductions.

Virginia Department of Taxation — 2026 Employer's Withholding Guide

Source for Virginia's progressive bracket structure: 2% ($0–$3,000), 3% ($3,001–$5,000), 5% ($5,001–$17,000), 5.75% (above $17,000). Standard deduction: $8,500 (single).

Massachusetts Department of Revenue — Form M-4 and Withholding Guide

Source for Massachusetts's 5% flat income tax rate. The 4% surtax on income above $1 million (the "Fair Share Amendment" / Prop. 1) enacted in 2022 applies only above that threshold.

Arizona Department of Revenue — 2026 Withholding Tables

Source for Arizona's 2.5% flat rate, effective for tax year 2023 onward under HB 2900 (2021). The lowest flat income tax rate of any US state that taxes wages.

Colorado Department of Revenue — DR 1098 Withholding Tables

Source for Colorado's 4.4% flat rate. Colorado's TABOR (Taxpayer's Bill of Rights) provisions require excess revenue to be returned to taxpayers when applicable.

Washington State Employment Security Department

Source for the WA Cares Fund long-term care payroll deduction rate (0.58% of gross wages). Established under ESSB 1323 (2019, amended 2022).