Methodology & Sources

Where the numbers come from

All bracket thresholds, deductions, and limits are transcribed from primary IRS publications. We do not estimate or interpolate government figures.

• IRS Rev. Proc. 2026-35 — 2027 inflation adjustments
• IRS Rev. Proc. 2025-32 — 2026 inflation adjustments
• IRS — Federal income tax rates and brackets (Rev. Proc. 2024-40)
• IRS — Working Families Tax Cuts: individuals and workers
• IRS — Q&A on the deduction for qualified overtime compensation
• IRS — Schedule 1-A, Additional Deductions
• IRS — Check your eligibility for the enhanced deduction for seniors
• IRS — New and enhanced deductions for individuals
• IRS — 401(k) limit increases to $24,500 for 2026 (Notice 2025-67)
• IRS — COLA increases for dollar limitations on benefits and contributions

What the calculators do

• Tax calculators apply the marginal rate table to taxable income and report marginal and effective rates. They do not model credits, AMT, NIIT, or state tax.
• Paycheck calculator annualizes per-period gross pay, subtracts pre-tax deductions and the standard deduction, applies the bracket table, and adds employee FICA. It does not model W-4 allowances or state withholding.
• Deduction calculators apply the statutory caps and MAGI phase-outs for the Schedule 1-A deductions as described in IRS guidance.

Update policy

Figures are updated when the IRS publishes annual inflation adjustments (usually October–November for brackets and November for retirement limits) and when new guidance changes how a deduction works. Each page shows the publication year of its data.