Methodology and sources
Rate table version 2026-10-26.1, generated 2026-10-26. Every number in the calculator comes from one data file. If a figure for your tax year is not published yet, the calculator uses the newest earlier year and says so on screen.
How the estimate is built
- Net profit = gross 1099 income minus vehicle deduction (standard mileage or your business share of actual costs, plus parking and tolls) minus operating write-offs. A loss is carried through.
- Self-employment tax = 12.4% Social Security (up to the wage base, with W-2 wages using the base first) + 2.9% Medicare + 0.9% Additional Medicare above the filing-status threshold, all on 92.35% of net profit. Half of the Social Security and Medicare parts is deducted from income.
- Adjusted gross income = W-2 wages + net profit − half of SE tax − self-employed health insurance (capped at net profit minus half of SE tax) − retirement contributions.
- Federal income tax = progressive brackets on AGI minus the standard deduction, the qualified tips deduction and the 20% business income deduction (QBI), minus the child tax credit (limited to the tax owed).
- State income tax = the state's flat rate or brackets applied to AGI minus the state standard deduction where we have it.
- Balances: W-2 federal withholding only offsets federal income tax, W-2 state withholding only offsets state tax, and self-employment tax payments only offset self-employment tax. This is deliberately conservative; on a real return the IRS nets them together.
What is not modelled
- Wage and property limits on the QBI deduction above the threshold (flagged, not applied) and the new $400 minimum.
- The refundable child tax credit, earned income credit, and other credits.
- Local income taxes, state credits, and state standard deductions we could not source (a notice appears when this affects you).
- Head of household and separate-filer bracket schedules for states other than the federal ones.
- Retirement plan contribution limits.
Data tiers
Official means read directly from the IRS, SSA or a state agency. Statutory means set by law. Secondary means a reputable summary of an official source where the official page was not reachable; secondary figures that overlap were cross-checked against each other.
Sources
| Source | Tier | Retrieved |
|---|---|---|
| SSA — Contribution and Benefit Base Social Security taxable maximum: $176,100 (2025), $184,500 (2026). | official | 2026-10-26 |
| IRS IR-2025-128 — 2026 business standard mileage rate 72.5 cents 72.5 cents effective Jan 1, 2026, up 2.5 cents from 70 cents in 2025. | official | 2026-10-26 |
| IRS Announcement 2026-11 (reported by CPA Practice Advisor, Jul 16 2026) — 76 cents from Jul 1 2026 Mid-year increase to 76 cents. Cross-checked against Everlance and IFEBP summaries; the primary IRS notice page was not on the fetch allowlist. | secondary | 2026-10-26 |
| KPMG TaxNewsFlash — Rev. Proc. 2025-32 inflation adjustments for 2026 Single and MFJ brackets and standard deductions. IRS Rev. Proc. 2025-32 itself was not on the fetch allowlist. | secondary | 2026-10-26 |
| Journal of Accountancy — Annual inflation adjustments announced for tax year 2026 Independent confirmation of single/MFJ brackets and the standard deduction for all statuses. | secondary | 2026-10-26 |
| NerdWallet — 2026 tax brackets Head of household and married-filing-separately bracket thresholds (not in the KPMG or JofA pages). Single and MFJ rows matched KPMG and JofA exactly. | secondary | 2026-10-26 |
| Kiplinger — Child Tax Credit 2025 and 2026 $2,200 per child, $1,700 refundable cap (not modelled), phase-out $200,000 / $400,000, $50 per $1,000. | secondary | 2026-10-26 |
| SDO CPA — QBI calculator for 2025 and 2026 (cites Rev. Proc. 2025-32) Section 199A thresholds $201,775 single/HOH and $403,500 MFJ; post-OBBBA phase-in ranges $75,000 / $150,000. | secondary | 2026-10-26 |
| IRC §224 — Qualified tips deduction (statute text) $25,000 cap; phase-out starts at modified AGI $150,000 (joint $300,000), reduced $100 per $1,000; married must file jointly. | statutory | 2026-10-26 |
| Thomson Reuters — Final rule on tips deduction released (T.D. 10044) Final regulations list app/platform-based delivery workers and taxi/rideshare drivers as eligible occupations. | secondary | 2026-10-26 |
| IRS — What is the Additional Medicare Tax and who pays it 0.9% above $200,000 single/HOH, $250,000 MFJ, $125,000 MFS. Archival IRS page; thresholds are set by statute and not indexed. | official | 2026-10-26 |
| IRS — Estimated taxes Safe harbor: pay 90% of current-year tax or 100% of prior-year tax, whichever is smaller; no penalty if you owe under $1,000. The 110% higher-income rule is in Publication 505 (not fetched), so it carries the statutory tier. | official | 2026-10-26 |
| Self-employment tax — IRC §1401 and Schedule SE 12.4% Social Security, 2.9% Medicare, 92.35% net-earnings factor, $400 filing floor. Constants set by statute; not fetched in this pass. | statutory | n/a |
| Tax Foundation — State individual income tax rates and brackets, 2026 Rates and brackets as of Jan 1 2026. Excludes local income taxes. Single and MFJ schedules for graduated states. | secondary | 2026-10-26 |
| California FTB — Estimated tax payments California installments are 30% / 40% / 0% / 30% (Apr 15, Jun 15, Sep 15, Jan 15). | official | 2026-10-26 |
| California FTB — Standard deduction 2025 amounts only on the official page: $5,706 single/MFS, $11,412 MFJ/HOH. Used as the fallback for 2026 and 2027. | official | 2026-10-26 |
| New York DTF — Standard deductions 2025 amounts: $8,000 single/MFS, $16,050 MFJ, $11,200 HOH. Not indexed for inflation. | official | 2026-10-26 |
| Our Tax Partner — 2026 state standard deductions North Carolina 2026: $12,750 single, $25,500 MFJ. Single secondary source, not cross-checked against NCDOR. | secondary | 2026-10-26 |
When figures change
The IRS usually publishes next year's inflation adjustments in October or November and the standard mileage rate in December. Until then the calculator shows a warning and uses the latest published year. Spotted something wrong? Tell us with the figure and its source.