Methodology

The math, the constants, and the assumptions behind every output on this site. If something looks off, this is the page that explains why.

Federal income tax

Calculations use the 2026 projected federal brackets, inflation- adjusted forward from the 2025 IRS values published in Rev. Proc. 2024-40. The standard deduction defaults are $15,700 (single), $31,400 (married filing jointly), $15,700 (married filing separately), and $23,550 (head of household). When the IRS publishes its official 2026 inflation procedure, this page is updated within a week and the change appears in the changelog below.

FICA

Social Security is 6.2% on wages up to the projected 2026 wage base of $178,500. Medicare is 1.45% on all wages, with an additional 0.9% surtax on combined wages above the filing-status threshold ($200,000 single, $250,000 married joint, $125,000 married separate, $200,000 head of household). The calculator applies the surtax automatically when relevant.

Self-employment tax

Net SE earnings are multiplied by 92.35% to get SE-taxable income. Social Security (12.4%) applies up to the wage base, reduced by any W-2 wages already counted there. Medicare (2.9%) applies to all SE-taxable earnings with no cap. Half of the Social Security plus Medicare portion (not the Additional Medicare 0.9%) is deductible above the line on Schedule 1.

State income tax

Texas charges $0 on personal income. There is no SDI, no local wage tax, and no franchise tax that touches individual W-2 or 1099 income. State-comparison pages use each state’s 2026 projected bracket structure where published, with our best inflation projection where the state’s schedule has not yet been released.

Bonus and supplemental withholding

The IRS percentage method applies: 22% federal withholding on supplemental wages up to $1M YTD, 37% above. FICA stacks on top, subject to whether year-to-date wages have crossed the SS wage base. The bonus calculator handles the SS-already-capped case automatically.

Pre-tax contributions

Traditional 401(k) reduces federal taxable income but not FICA wages. Section 125 contributions (HSA, qualifying health premiums, dependent-care FSA) reduce both federal taxable income and FICA wages, which is why HSAs are often the most tax-advantaged dollar a Texas earner can put away. Roth 401(k) and after-tax 401(k) are post-tax and don’t reduce federal taxable income.

Sources

• IRS Rev. Proc. 2024-40 — 2025 inflation methodology projected to 2026.
• IRS Notice 2024-XX — Social Security wage base and FICA thresholds for 2026.
• Texas Comptroller — sales tax base 6.25%, local additions up to 2% (combined cap 8.25%).
• Texas Workforce Commission — minimum wage tracks federal $7.25; no state-mandated overtime above FLSA.
• Bureau of Economic Analysis & Census ACS — household income, cost-of-living references.
• Texas county appraisal districts — effective property tax rates cited on city pages.

Texas does not have a state income tax statute, so there are no state-revenue sources on the income line.

Update log

• 2026-05-07 · Sharpened SERP metadata across all pages. Tightened titles to 45–55 characters and rewrote descriptions for click-through.
• 2026-04-14 · Updated 2026 federal brackets to the IRS revised inflation factor. No bracket boundaries shifted by more than a few hundred dollars.
• 2026-03-27 · Added Additional Medicare tax handling at $200k single and $250k joint thresholds. Bonus calculator now correctly accounts for the surtax when year-to-date wages exceed the threshold.
• 2026-02-19 · Fixed SE tax base. The engine now correctly uses 92.35% of net SE income (not 100%) as the self-employment tax base, matching Schedule SE line 4.
• 2026-01-08 · Released initial 2026 projections. All calculators carried forward 2025 values with the IRS inflation methodology applied.

Known limitations

The calculators on this site are deliberately scoped. Several real tax mechanics are not modeled because they are too individualized to estimate well in a generic tool.

• ISO AMT — incentive stock option exercises that trigger Alternative Minimum Tax. The calculation is highly personal and almost always needs a CPA.
• Multi-state apportionment — partial-year residents and people who travel for work owe state tax based on workdays sourced to each state. The calculators assume a single state of residence.
• EITC and child tax credits — refundable credits that affect filing outcomes more than withholding, and depend heavily on dependents, AGI, and other thresholds.
• Itemized deductions beyond a manual override — mortgage interest, the SALT cap, charitable giving. The calculator accepts a manual itemized total but doesn’t compute one for you.
• Wage garnishments — court-ordered child support, student loan administrative wage garnishment, and tax levies all reduce net pay outside the standard payroll math.
• RSU sell-to-cover and lot-level cost basis — the calculator treats RSU vests as ordinary wage income, which they are at vest. Capital gains on subsequent sales depend on holding period and basis tracking.
• Net Investment Income Tax (3.8%) — applies to certain investment income above the AGI threshold. The calculators are wage-focused.
• Alternative employer fringe benefits — qualified transportation, employer student-loan repayment under §127, adoption assistance, etc. All are real, none are modeled.

For anything in the list above, please consult a Texas-licensed CPA or tax attorney. The estimates on this site are educational and not a substitute for professional advice.

Disclaimer

Estimates are educational. Nothing on this site is tax, legal, or financial advice. For filing your return, planning equity compensation, or handling a residency audit, hire a licensed professional. Material errors should be reported to hello@texastaxcalculator.com and will appear in the change log above when corrected.