RefundPlot 2026 constants · status-tracked

Methodology

This page is the site's trust contract: every formula in every calculator, listed; every constant, sourced; every update, logged. It exists because the tax-calculator industry has a documented staleness problem — major tools running years-old bracket tables, a widely used one getting the home-sale exclusion wrong — and the only durable answer is showing our work in the open. The short version of our methodology is reproducibility — same inputs, same outputs, every intermediate step expandable — plus honest labeling of anything not yet verified against a primary IRS document.

Federal income tax (federal-income-tax-calculator, tax-refund-calculator): taxable income = wages − pre-tax contributions − deduction; tax = marginal bracket sum across the seven-rate structure; credits subtract last. Verified anchor: 2025 single, $50,000 wages − $15,000 standard deduction = $35,000 taxable → $3,961.50 tax, matching an independent long-running calculator's output.

FICA: Social Security 6.2% (capped at the annual wage base) + Medicare 1.45% = 7.65% combined. Verified anchor: $50,000 wages → $3,825. FICA never participates in refund math — it is displayed separately on purpose.

Refund split (tax-refund-calculator): refund = (liability − federal income tax withheld − nonrefundable credits) + refundable credits (EITC/CTC/ACTC). The two components are displayed separately because they behave completely differently (adjustable withholding vs claim-at-filing credits).

W-4 withholding (tax-withholding-calculator): projected annual wages from YTD paystubs + remaining paychecks; four levers applied with units (Step 3/4a/4b annual, 4c per paycheck); two-jobs rate branch; bonus 22% flat-withholding gap mode.

Capital gains (capital-gains-tax-calculator): basis = cost + acquisition costs; ST/LT split at greater than 365 days; class-internal netting then cross-netting; annual loss cap $3,000 with indefinite carryforward; LTCG three-tier rates; §121 exclusion locked at the statutory $250,000 / $500,000 (a known competitor error — our tests pin the legal values).

Self-employment tax (self-employment-tax-calculator): base = 92.35% of net SE income; tax = 15.3% (12.4% Social Security up to the wage base, coordinated with W-2 wages + 2.9% Medicare); half deductible above the line. Verified anchor: $100,000 → $14,130.

Estimated tax (estimated-tax-calculator): safe harbor = prior-year total tax × 100% (× 110% if prior-year AGI > $150,000, $75,000 MFS); current-year estimate compared; quarterly schedule mapped to the four IRS due dates.

State tax (state-tax-calculator): per-state bracket tables for ten maintained states (CA, NY, NJ, PA, IL, OH, GA, TX, FL, WA), no-income-tax states explicitly branched, unsupported states explicitly labeled rather than defaulted.

  • IRS annual revenue procedures (federal bracket thresholds, by year)
  • IRS Publication 505 (withholding and estimated tax)
  • IRS Publication 523 (selling your home / §121)
  • Schedule SE and Form 1040-ES instructions
  • Schedule D and Form 1040 instructions (netting and the qualified dividends and capital gains tax worksheet)
  • Verification anchors: cross-calculator agreement on the 2025 examples above ($3,961.50; $3,825; $14,130)

2026 constants (federal brackets, LTCG breakpoints, standard deduction) are currently marked "pending IRS first-hand verification." They rest on agreement across multiple independent implementations, not yet on our own line-by-line check of the primary IRS document. We publish them labeled rather than silently stale or silently unverified, and remove the label — with a changelog entry — when verification completes. The 2025 anchors above are fully verified.

| Date | Page | Change | Source | |---|---|---|---| | 2026-10-26 | all | Initial 16-page launch: 8 calculators, 6 guides, about, methodology. 2026 constants published with pending-verification labels; 2025 anchors verified by cross-calculator agreement. | launch baseline | | YYYY-MM-DD | page slug | constant/formula updated (old → new) | IRS document + verification date |

Every calculator produces an estimate for planning purposes. It is not tax advice, and it is not a substitute for filing an accurate return.

## Full constants register

| Page | Constant | Source | Status | |---|---|---|---| | federal-income-tax-calculator | 2026 联邦税率档（single 12,400/50,400/105,700/201,775/256,225/640,600 等四身份） | Cross-verified across resideline JS + moneychimp tax_rates.js + freetaxusa | competitor-corroborated | | federal-income-tax-calculator | 2025 联邦税率档（single 11,925/48,475/103,350/197,300/250,525/626,350） | Behavior-verified against thetaxcalculator ($50k → $3,961.50) + moneychimp + freetaxusa | competitor-corroborated | | tax-refund-calculator | 2025 标准扣除 single $15,000 | Cross-checked against thetaxcalculator | competitor-corroborated | | tax-refund-calculator | 2026 标准扣除 single $15,750（估计） | Competitor estimate — none of the 13 reviewed sites is IRS first-hand verified | pending | | tax-refund-calculator | 2025 SS wage base $176,100 | SSA announcement (2025); 2026 pending SSA release | competitor-corroborated | | tax-refund-calculator | SS 6.2% + Medicare 1.45%（Medicare 附加 0.9% >$200k 为 V2） | IRC §3101/§3111 (statutory rates, stable long-term) | verified | | capital-gains-tax-calculator | 2026 LTCG 档（0%≤49,450/98,900(MFJ)，15%≤545,500/613,700，20%+） | Cross-verified in resideline JS | competitor-corroborated | | capital-gains-tax-calculator | §121 home-sale exclusion: single $250,000 / MFJ $500,000 (statutory, locked against regression) | 26 U.S.C. §121(b)(2) statutory value (competitor resideline shows $200k/$250k — a verified error) | verified | | self-employment-tax-calculator | SE tax 15.3% × 92.35% base + 半额扣除回减（$100k→$14,130） | IRC §1401 + Schedule SE; corroborated across competitors | verified | | estimated-tax-calculator | Safe harbor：上年税 100% / AGI>$150k 用 110% | IRC §6654(d); IRS Publication 505 (section number pending first-hand check) | competitor-corroborated | | tax-withholding-calculator | Bonus 22% flat 预扣 | IRC §3402(a) supplemental wage flat 22% (under $1M) | verified | | tax-refund-calculator | OBBBA：tips $25k / overtime $12.5k / car interest / QBI 20% / CTC $2,200（ACTC $1,700） | OBBBA as transcribed by competitor implementations; IRS guidance pending | pending | | state-tax-calculator | 10 州档表（CA/NY/NJ/PA/IL/OH/GA + TX/FL/WA 免税） | State revenue department tables as transcribed; corroborated across competitors | competitor-corroborated |

## Changelog

  • 2026-10-26 — Initial release. Constants listed with verification status; primary-source (IRS) verification in progress.