Published verification · Tax year 2026

Accuracy Report

Most tax sites ask you to trust their experts. We publish our math instead. Every case below was hand-derived on paper from the cited IRS, SSA, and state publications — independent of our code — then run against the live calculator engine that powers every page on this site. Open any case, check our arithmetic, and audit the auditor.

Latest run

25/25checks passed

Engine output matches every hand-derived value within ±$0.01 (±0.05% for rates). Last full re-derivation: October 31, 2026.

2026

tax year

100%

open math

How this works

1Derive on paper. Each expected value is computed by hand from the primary publication — IRS Rev. Proc. 2025-32 for federal brackets and standard deductions, the SSA 2026 fact sheet for the wage base, and each state’s own rate schedule — without touching our engine.
2Run the engine. The production functions that power the site’s calculators — calculateFederalTax, calculateFICA, calculateStateTax, calculatePaycheck — execute each case live on this page.
3Compare in the open. Both numbers are printed side by side with the full step-by-step derivation, so you can re-do the math yourself in under a minute per case.

What this is not. These checks verify our math against published rates — they are not tax advice, and they deliberately exclude situation-specific items (itemized deductions, credits, multi-state work, local taxes outside NYC). Our calculators produce planning estimates, not filed returns. See the full methodology for every assumption and edge case we make.

Federal Income Tax

9/9 passed

Progressive bracket math against IRS Rev. Proc. 2025-32, across all four filing statuses.

Gross below the standard deduction → zero tax

$15,000 gross · Single · standard deduction

$0.00

FED-001 · PASS

Source

IRS Rev. Proc. 2025-32 (standard deduction $16,100, Single)

Hand derivation (paper math)

Taxable income = $15,000 − $16,100 = $0 (floored at zero). No bracket is entered. Tax = $0.00.

expected: $0.00engine: $0.00tolerance: ±$0.01

Second bracket (12%) — $30,000 Single

$30,000 gross · Single · standard deduction

$1,420.00

FED-002 · PASS

Source

IRS Rev. Proc. 2025-32 (10% to $12,400; 12% to $50,400)

Hand derivation (paper math)

Taxable = $30,000 − $16,100 = $13,900. 10% × $12,400 = $1,240.00; 12% × ($13,900 − $12,400 = $1,500) = $180.00. Total = $1,420.00.

expected: $1,420.00engine: $1,420.00tolerance: ±$0.01

Mid 12% bracket — $50,000 Single

$50,000 gross · Single · standard deduction

$3,820.00

FED-003 · PASS

Source

IRS Rev. Proc. 2025-32

Hand derivation (paper math)

Taxable = $33,900. 10% × $12,400 = $1,240.00; 12% × $21,500 = $2,580.00. Total = $3,820.00.

expected: $3,820.00engine: $3,820.00tolerance: ±$0.01

Third bracket (22%) — $75,000 Single

$75,000 gross · Single · standard deduction

$7,670.00

FED-004 · PASS

Source

IRS Rev. Proc. 2025-32 (22% starts at $50,400)

Hand derivation (paper math)

Taxable = $58,900. $1,240.00 + $4,560.00 (12% × $38,000) + 22% × ($58,900 − $50,400 = $8,500) = $1,870.00. Total = $7,670.00.

expected: $7,670.00engine: $7,670.00tolerance: ±$0.01

Deep 22% bracket — $100,000 Single

$100,000 gross · Single · standard deduction

$13,170.00

FED-005 · PASS

Source

IRS Rev. Proc. 2025-32

Hand derivation (paper math)

Taxable = $83,900. $1,240.00 + $4,560.00 + 22% × $33,500 = $7,370.00. Total = $13,170.00.

expected: $13,170.00engine: $13,170.00tolerance: ±$0.01

Fourth bracket (24%) — $200,000 Single

$200,000 gross · Single · standard deduction

$36,734.00

FED-006 · PASS

Source

IRS Rev. Proc. 2025-32 (24% band $105,700–$201,775)

Hand derivation (paper math)

Taxable = $183,900. $1,240.00 + $4,560.00 + 22% × $55,300 = $12,166.00 + 24% × $78,200 = $18,768.00. Total = $36,734.00.

expected: $36,734.00engine: $36,734.00tolerance: ±$0.01

Top bracket (37%) — $1,000,000 Single

$1,000,000 gross · Single · standard deduction

$320,000.25

FED-007 · PASS

Source

IRS Rev. Proc. 2025-32 (37% above $640,600)

Hand derivation (paper math)

Taxable = $983,900. Bands: $1,240.00 + $4,560.00 + $12,166.00 + $23,058.00 (24% × $96,075) + $17,424.00 (32% × $54,450) + $134,531.25 (35% × $384,375) + $127,021.00 (37% × $343,300). Total = $320,000.25.

expected: $320,000.25engine: $320,000.25tolerance: ±$0.01

Married filing jointly — $150,000 MFJ

$150,000 gross · MFJ · standard deduction

$15,340.00

FED-008 · PASS

Source

IRS Rev. Proc. 2025-32 (MFJ: $32,200 deduction; 22% starts at $100,800)

Hand derivation (paper math)

Taxable = $150,000 − $32,200 = $117,800. 10% × $24,800 = $2,480.00; 12% × $76,000 = $9,120.00; 22% × $17,000 = $3,740.00. Total = $15,340.00.

expected: $15,340.00engine: $15,340.00tolerance: ±$0.01

Head of household — $80,000 HoH

$80,000 gross · Head of Household · standard deduction

$6,348.00

FED-009 · PASS

Source

IRS Rev. Proc. 2025-32 (HoH: $24,150 deduction; 12% to $67,450)

Hand derivation (paper math)

Taxable = $80,000 − $24,150 = $55,850. 10% × $17,700 = $1,770.00; 12% × $38,150 = $4,578.00. Below the $67,450 22% threshold. Total = $6,348.00.

expected: $6,348.00engine: $6,348.00tolerance: ±$0.01

FICA (Social Security & Medicare)

5/5 passed

Employee-share payroll taxes, the 2026 wage base, and the 0.9% additional Medicare surtax.

Typical wage — $75,000 Single

$75,000 wages · employee share only

$5,737.50

FICA-001 · PASS

Source

SSA 2026 fact sheet: OASDI 6.2% (base $184,500); Medicare 1.45%

Hand derivation (paper math)

Social Security = 6.2% × $75,000 = $4,650.00. Medicare = 1.45% × $75,000 = $1,087.50. No additional Medicare (below $200K). Total = $5,737.50.

expected: $5,737.50engine: $5,737.50tolerance: ±$0.01

Exactly at the wage base — $184,500

$184,500 wages · employee share only

$14,114.25

FICA-002 · PASS

Source

SSA 2026 fact sheet (wage base $184,500)

Hand derivation (paper math)

SS = 6.2% × $184,500 = $11,439.00 (cap reached — nothing above is taxed for SS). Medicare = 1.45% × $184,500 = $2,675.25. Total = $14,114.25.

expected: $14,114.25engine: $14,114.25tolerance: ±$0.01

Exactly at the surtax threshold — $200,000 Single

$200,000 wages · employee share only

$14,339.00

FICA-003 · PASS

Source

IRC §3101(b)(2) (0.9% above $200K, not indexed)

Hand derivation (paper math)

SS = $11,439.00 (capped). Medicare = 1.45% × $200,000 = $2,900.00. Additional 0.9% applies only ABOVE $200,000 → $0 at exactly $200,000. Total = $14,339.00.

expected: $14,339.00engine: $14,339.00tolerance: ±$0.01

Surtax + cap — $300,000 Single

$300,000 wages · employee share only

$16,689.00

FICA-004 · PASS

Source

SSA 2026 fact sheet + IRC §3101(b)(2)

Hand derivation (paper math)

SS = $11,439.00 (cap). Medicare = $4,350.00. Additional = 0.9% × ($300,000 − $200,000) = $900.00. Total = $16,689.00.

expected: $16,689.00engine: $16,689.00tolerance: ±$0.01

MFJ surtax threshold — $500,000 Married

$500,000 wages · MFJ · employee share only

$20,939.00

FICA-005 · PASS

Source

IRC §3101(b)(2) (MFJ threshold $250,000)

Hand derivation (paper math)

SS = $11,439.00 (cap). Medicare = 1.45% × $500,000 = $7,250.00. Additional = 0.9% × ($500,000 − $250,000) = $2,250.00. Total = $20,939.00.

expected: $20,939.00engine: $20,939.00tolerance: ±$0.01

State Income Tax

6/6 passed

Progressive, flat, and zero-tax state engines against each state’s published schedule.

Illinois flat tax — $75,000 Single

$75,000 gross · IL (flat 4.95%, $2,925 exemption)

$3,567.71

ST-IL-001 · PASS

Source

IL Income Tax Act (35 ILCS 5/203) — 4.95% + personal exemption

Hand derivation (paper math)

IL has no standard deduction. Taxable = $75,000 − $2,925 = $72,075. Tax = 4.95% × $72,075 = $3,567.71.

expected: $3,567.71engine: $3,567.71tolerance: ±$0.01

California progressive — $100,000 Single

$100,000 gross · CA (std. deduction $6,083)

$5,381.13

ST-CA-001 · PASS

Source

CA FTB 2026 bracket schedule (1% → 13.3%)

Hand derivation (paper math)

Taxable = $93,917. 1%×$10,412=$104.12; 2%×$14,272=$285.44; 4%×$14,275=$571.00; 6%×$15,422=$925.32; 8%×$13,969=$1,117.52; 9.3%×$25,567=$2,377.73. Total = $5,381.13.

expected: $5,381.13engine: $5,381.13tolerance: ±$0.01

California top-bracket territory — $250,000 Single

$250,000 gross · CA (std. deduction $6,083)

$19,331.13

ST-CA-002 · PASS

Source

CA FTB 2026 bracket schedule (9.3% to $349,137)

Hand derivation (paper math)

Taxable = $243,917. Brackets through 8% = $3,003.40; 9.3% × ($243,917 − $68,350 = $175,567) = $16,327.73. Total = $19,331.13.

expected: $19,331.13engine: $19,331.13tolerance: ±$0.01

New York progressive — $75,000 Single

$75,000 gross · NY (std. deduction $8,000)

$3,453.00

ST-NY-001 · PASS

Source

NYS DTF 2026 rate schedule (3.9% → 10.9%)

Hand derivation (paper math)

Taxable = $67,000. 3.9%×$8,500=$331.50; 4.4%×$3,200=$140.80; 5.15%×$2,200=$113.30; 5.4%×$53,100=$2,867.40. Total = $3,453.00.

expected: $3,453.00engine: $3,453.00tolerance: ±$0.01

Texas — zero income tax at any income

$100,000 gross · TX

$0.00

ST-TX-001 · PASS

Source

TX Constitution Art. 8 §24 (no state income tax)

Hand derivation (paper math)

Texas levies no personal income tax. Tax = $0.00 at every income level.

expected: $0.00engine: $0.00tolerance: ±$0.01

Florida — zero income tax at any income

$100,000 gross · FL

$0.00

ST-FL-001 · PASS

Source

FL Constitution Art. VII §11 (no state income tax)

Hand derivation (paper math)

Florida levies no personal income tax. Tax = $0.00 at every income level.

expected: $0.00engine: $0.00tolerance: ±$0.01

Full Paycheck Integration

5/5 passed

End-to-end take-home pay: federal + FICA + state stacked together, per pay period.

High-tax state: $75,000 Single in California (monthly)

$75,000 · Single · CA · monthly pay · no pre-tax deductions

$58,536.37

INT-001 · PASS

Source

Rev. Proc. 2025-32 + SSA 2026 + CA FTB 2026 (composite)

Hand derivation (paper math)

Federal $7,670.00 + FICA $5,737.50 + CA $3,056.13 (taxable $68,917) = $16,463.63 total. Net annual = $58,536.37 → $4,878.03/month.

expected: $58,536.37engine: $58,536.37tolerance: ±$0.01

Zero-tax state: $60,000 Married in Texas (biweekly)

$60,000 · MFJ · TX · biweekly pay · no pre-tax deductions

$2,021.92

INT-002 · PASS

Source

Rev. Proc. 2025-32 + SSA 2026 (composite)

Hand derivation (paper math)

Federal (taxable $27,800) = $2,840.00 + FICA $4,590.00 + TX $0 = $7,430.00. Net annual = $52,570.00 → $2,021.92 per biweekly paycheck.

expected: $2,021.92engine: $2,021.92tolerance: ±$0.01

Flat-tax state: $95,000 Single in Illinois (monthly)

$95,000 · Single · IL · monthly pay · no pre-tax deductions

$5,925.40

INT-003 · PASS

Source

Rev. Proc. 2025-32 + SSA 2026 + 35 ILCS 5/203 (composite)

Hand derivation (paper math)

Federal $12,070.00 + FICA $7,267.50 + IL $4,557.71 = $23,895.21. Net annual = $71,104.79 → $5,925.40/month.

expected: $5,925.40engine: $5,925.40tolerance: ±$0.01

High-cost state: $120,000 Single in New York (monthly)

$120,000 · Single · NY · monthly pay · no pre-tax deductions

$7,267.52

INT-004 · PASS

Source

Rev. Proc. 2025-32 + SSA 2026 + NYS DTF 2026 (composite)

Hand derivation (paper math)

Federal $17,570.00 + FICA $9,180.00 + NY $6,039.75 = $32,789.75. Net annual = $87,210.25 → $7,267.52/month.

expected: $7,267.52engine: $7,267.52tolerance: ±$0.01

Effective-rate sanity: $75,000 Single in CA

$75,000 · Single · CA — total tax ÷ gross

21.95%

INT-005 · PASS

Source

Derived from INT-001 components

Hand derivation (paper math)

($7,670.00 + $5,737.50 + $3,056.13) ÷ $75,000 = 21.95% effective rate.

expected: 21.95%engine: 21.95%tolerance: ±0.05%

Primary sources

Every derivation above traces to one of these documents. Click through and check us.

Full methodology →

Every rate we use, every assumption we make, and the edge cases these checks don’t cover.

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