Freelancer Tax Calculation: Sources and the Full Formula

The sources, figure by figure

The tool's 2026 figures come from primary publications, not from aggregator summaries. Where a secondary source once circulated a stale number, this guide follows the primary source: the QBI phase-out ranges below, for example, follow Revenue Procedure 2025-32, not older third-party tables that still show superseded thresholds.

A note on the last row, because it is where over-claiming usually happens. Recent legislation (the One Big Beautiful Bill Act, OBBBA) added a minimum QBI deduction amount, but its applicability is unverified for this tool's computation, so it is not added to any figure in this guide or in the tool. The only statement this guide makes about it is this one: OBBBA added a minimum deduction amount, and its specific application should be confirmed against the IRS Form 8995 instructions. Anything more precise would be a guess dressed as a source.

Estimates only — not tax advice. This guide documents a planning calculation for 2026 federal tax. It does not model state tax, credits, or filing statuses beyond single and married filing jointly in version 1. Consider consulting a CPA for your situation.

The formula chain, step by step

The calculation runs in six steps, in this order. Each step feeds the next, and the order matters: the deductible half of self-employment tax, for example, must be computed before AGI, because AGI subtracts it, and the QBI deduction must be computed after AGI, because it is capped by taxable income before the QBI deduction.

Net income = total 1099 income − business expenses

Taxable self-employment income = net income × 92.35%

Self-employment tax = min(taxable self-employment income, max(0, $184,500 − W-2 wages)) × 12.4% + taxable self-employment income × 2.9% (+ 0.9% on the part of combined income above $200,000 single / $250,000 married filing jointly)

AGI = net income + W-2 wages + expected other income − half of self-employment tax

QBI deduction = min(20% × (net income − half of self-employment tax), 20% × (AGI − standard deduction))

Taxable income = AGI − standard deduction − QBI deduction, then taxed at the 2026 brackets

Two details in the chain deserve emphasis. First, the Social Security part of self-employment tax is capped twice over: by the wage base itself ($184,500) and by the room left under it after W-2 wages, which is why the tool asks for W-2 wages at all. The Medicare part has no cap. Second, the QBI deduction is a minimum of two 20% figures, not a flat 20% of anything: 20% of QBI (net income minus the deductible half of self-employment tax) and 20% of taxable income before the QBI deduction (AGI minus the standard deduction). Whichever is smaller wins, and at lower incomes the second figure is usually the binding one.

2026 brackets and standard deductions

The 2026 federal income tax brackets and standard deductions below are from Revenue Procedure 2025-32, as announced in IRS news release IR-2025-103. They apply to taxable income — the figure left after the standard deduction and the QBI deduction — not to gross income, which is why a freelancer with $60,000 of income is not taxed at the rate that appears next to $60,000 in any bracket table.

The 2026 standard deductions are $16,100 for single filers and $32,200 for married filing jointly. The head-of-household standard deduction of $24,150 is noted here only because readers ask about it: that filing status is not modelled in version 1 of the tool, and it will be added as a tool feature later rather than smuggled into version 1 results. Do not use the single or joint figures as a proxy for a head-of-household return.

Self-employment tax in detail

Self-employment tax has three parts, and they behave differently. Social Security tax is 12.4% of taxable self-employment income, but only up to the 2026 Social Security wage base of $184,500 from the SSA 2026 COLA Fact Sheet, with W-2 wages using up that room first. Medicare tax is 2.9% of all taxable self-employment income, with no cap. The additional Medicare tax is 0.9% on the part of combined income above a threshold that is not indexed for inflation: $200,000 for single filers, $250,000 for married filing jointly, and $125,000 for married filing separately, with self-employment income and W-2 wages judged together.

The starting line is low and often missed: net self-employment income of $400 or more may mean self-employment tax is owed, even when income tax is not. Below $400 of net self-employment income, the tool charges no self-employment tax. That $400 line is about whether the tax applies at all; it has nothing to do with the $1,000 estimated-payment trigger or the $2,000 1099 reporting threshold, and the edge cases guide keeps the three figures apart.

The 92.35% factor is the other detail people trip over. It is not a discount; it is the arithmetic that removes the employer's half of payroll tax from the base before the combined rate is applied, mirroring the way employees are taxed only on wages net of nothing but never on the employer's contribution. Taxable self-employment income is therefore 92.35% of net income, and both the 12.4% and the 2.9% rates apply to that reduced figure.

The QBI deduction and the SSTB phase-out

The qualified business income deduction lets eligible freelancers deduct up to 20% of qualified business income, but the operative word is up to. The deduction is the smaller of 20% of QBI and 20% of taxable income before the QBI deduction, as the formula chain states. The common simplified version — 20% of net income — overstates the deduction whenever taxable income before the deduction is the smaller figure, which at ordinary freelance incomes it usually is. At $60,000 with no expenses, the simplified version gives a federal income tax of about $3,071; the correct smaller-of-two rule gives $3,559. The $488 gap is the cost of the shortcut, and it is the single most common error in third-party freelancer estimates.

For specified service trades or businesses (SSTBs) — the category that covers many professional freelancers — the deduction phases out over a taxable-income range, shrinking proportionally inside the range and reaching zero above it. The 2026 ranges, per Revenue Procedure 2025-32, are $201,750 to $276,750 for single filers and $403,500 to $553,500 for married filing jointly. Below the range the full deduction applies; inside it, the deduction is reduced in proportion to where taxable income falls in the range; above it, an SSTB deduction is zero. Older third-party tables showing lower thresholds are superseded and must not be used for 2026.

Whether a particular business is an SSTB, and whether other QBI limits apply, depends on the business's facts, and the tool applies the phase-out mechanically from taxable income. A freelancer near a phase-out boundary should treat the tool's figure as provisional and consider consulting a CPA: small income changes near the boundary move the deduction discontinuously, and the boundary is exactly where a planning estimate is most fragile.

Safe harbor and the quarterly due dates

Estimated tax is generally expected when expected tax due is $1,000 or more, and the penalty-safe amount is set by Form 1040-ES: generally 100% of last year's tax, paid in quarterly instalments. The exception that catches higher earners is the prior-year AGI test: when the prior year's AGI was above $150,000 (above $75,000 for married filing separately), the safe-harbor amount is 110% of last year's tax instead of 100%. The year in that sentence is the prior year, not the current year — the ratio for this year's payments is decided by last year's AGI.

Version 1 of the tool divides the estimated annual total into four equal payments on those dates. That is a planning simplification, and this guide states it plainly: equal quarters are not the safe-harbor computation. A freelancer whose income arrives unevenly, or who has a prior year to anchor to, should compare the equal-quarter plan against the safe-harbor amount and pay the larger of the two logics' demands where they differ. The how-to-use guide shows the quarterly plan on the $60,000 example.

Worked check: the $60,000 chain, line by line

The $60,000 example from the companion guides, single filer, no expenses, no W-2 wages, no other income, run through the chain with no rounding until the final lines:

Check the QBI line, because it is where shortcuts diverge: 20% of QBI ($60,000 minus the $4,239 half, or $55,761) is $11,152, while 20% of taxable income before the QBI deduction ($55,761 minus the $16,100 standard deduction, or $39,661) is $7,932. The smaller figure, $7,932, is the deduction. The federal income tax then follows the single brackets: 10% of the first $12,400 is $1,240, and 12% of the remaining $19,329 (from $12,400 to $31,729) is $2,319, giving $3,559. Every figure the tool prints for these inputs should match this table; if it does not, the tool, not this guide, should be questioned first, since this table is derived directly from the cited sources.

Update dates and the review cycle

Each figure in this guide carries its update date with it. The brackets, standard deductions and SSTB ranges are the 2026 figures from Revenue Procedure 2025-32, announced in IRS news release IR-2025-103 in late 2025. The wage base is the 2026 figure from the SSA 2026 COLA Fact Sheet, and the additional Medicare thresholds are the statutory figures in the IRS Additional Medicare Tax Q&A. The quarterly dates are the 2026 estimated-tax dates from Form 1040-ES. The $400 self-employment threshold, the $1,000 estimated-payment trigger and the safe-harbor percentages are the long-standing Form 1040-ES and Schedule SE rules as they apply to 2026.

The review cycle is annual and fixed: every January, after tax-law updates for the new year are published, each figure in this guide and in the tool is re-checked against the new revenue procedure, the new SSA fact sheet, and the new Form 1040-ES, and the guide's updated date moves to the review date. Mid-year IRS guidance that changes a figure triggers an out-of-cycle update, not a wait until January. Until a review happens, the figures above are the 2026 figures — do not carry them into another tax year without checking, and do not use 2025 figures (brackets, standard deductions, or the old $600 reporting threshold) as if they were 2026 figures.

State tax is absent from this guide for the same reason it is absent from version 1 of the tool: state rates and state due dates have not yet been verified against each state tax authority, and an unverified state figure is worse than an honestly missing one. When state verification is complete, this guide will gain a state section with its own source table, and the tool will gain a state input — in that order.