US tax calculators for the self-employed
Four free calculators for sole proprietors, freelancers and contractors, covering the four One Big Beautiful Bill Act deductions on Schedule 1-A, quarterly estimated tax safe harbors, and the S corp election. Every figure is taken from irs.gov and carries the date it was last checked.
Calculators
| Ref | Calculator | What it answers | Source |
|---|---|---|---|
| US-1 | Car Loan Interest Deduction Calculator | How much car loan interest you can deduct after the MAGI phaseout, if any. | irs.gov |
| US-2 | Schedule 1-A Combined Deduction Estimator | All four OBBBA above-the-line deductions and their total for Form 1040 line 13b. | irs.gov |
| US-3 | Quarterly Estimated Tax Calculator | Your four quarterly payments, and which safe harbor applies to you. | irs.gov |
| US-4 | Sole Proprietor vs S Corp Tax Calculator | Self-employment tax against payroll tax plus distributions, with the difference. | irs.gov |
The four Schedule 1-A deductions
The One Big Beautiful Bill Act created four above-the-line deductions, claimed together on Schedule 1-A and totalled to Form 1040 line 13b. They are available whether or not you itemize. Each has its own annual cap and its own modified adjusted gross income phaseout.
| Deduction | Annual cap |
|---|---|
| No tax on tips (Part II) | $25,000 |
| No tax on overtime (Part III) | $12,500 single / $25,000 MFJ |
| Car loan interest (Part IV) | $10,000 |
| Senior deduction (Part V) | $6,000 per person |
Each deduction phases out above a MAGI threshold, and the overtime rule catches people out: only the FLSA-required premium counts, not all overtime pay. To work out your own total, use the Schedule 1-A Combined Deduction Estimator.
When quarterly estimated tax is due
| Payment | Due |
|---|---|
| Q1 | |
| Q2 | |
| Q3 | |
| Q4 |
Guides
Longer explanations of the rules behind each calculator.
How these figures are checked
Every cap, threshold and date is taken directly from irs.gov, never from a summary or a third-party guide, and each calculator is tested against the IRS's own worked examples before it ships. The full process, and the verification date for each figure, is on the methodology and sources page. This site calculates and cites; it does not give tax advice.
Filing in the United Kingdom instead? See the UK calculators.