Free Freelancer Tax Calculators — US Self-Employment, UK IR35, Quarterly 1040-ES

Freelancers and contractors carry tax burdens W-2 employees never see. Self-employment tax doubling the FICA hit. Quarterly estimated payments with penalty deadlines. UK contractors navigating inside vs outside IR35. We shipped three calculators that model each scenario with real 2025-26 numbers.

All three are free, browser-only, no signup. Inputs never leave your device.

1. US Self-Employment Tax Calculator

Self-Employment Tax Calculator

US freelancers pay 15.3% SE tax on top of income tax — 12.4% for Social Security (wage-capped) + 2.9% for Medicare (uncapped) + Additional Medicare 0.9% above filing-status thresholds.

Inputs:

  • Net self-employment income
  • Filing status (single / married joint / married separate / HoH)
  • Additional W-2 wage income (reduces the SS-capped portion)

Outputs:

  • SE tax owed
  • Employer-equivalent deduction (half of SE tax is deductible above-the-line)
  • Effective SE tax rate
  • SS portion + Medicare portion breakdown
  • W-2-employee-comparable tax burden side-by-side

2025 figures baked in: SS wage base $176,100, 92.35% earnings adjustment (only 92.35% of net SE income is subject to SE tax — common mistake on manual calculations).

2. UK IR35 Calculator (Inside vs Outside)

IR35 Calculator

If you contract through a UK limited company, IR35 is the single biggest factor in your take-home.

  • Inside IR35 = deemed employment. PAYE + NI on the full contract rate. Umbrella company fee typically £20-25/week. Employer NI 15% deducted before you're paid.
  • Outside IR35 = legitimate B2B relationship. Your Ltd pays corporation tax 19% (small profits ≤£50k) or 25% main rate, then you extract via director salary (£12,570 tax-free) + dividends (8.75% / 33.75% / 39.35% thresholds).

The calculator runs both paths with your numbers and shows the annual delta.

Inputs: gross day rate (£), days/year, status (inside/outside), pension contribution (weekly), umbrella fee (inside IR35 only).

Outputs: side-by-side annual net take-home for both paths, personal allowance taper above £100k, marginal corporation tax relief for profits £50k-£250k.

Note: Scottish income tax bands differ from England/Wales/NI — that case is called out in the FAQ.

3. US Quarterly Tax Estimator (Form 1040-ES)

Quarterly Tax Estimator

IRS wants 90% of your current-year tax paid in during the year via withholding + estimated payments — OR 100% (110% if AGI >$150k) of last year's tax. Whichever is lower is the "safe harbor." Miss it and you pay underpayment penalties on top of the tax.

Inputs:

  • Projected annual freelance income + deductions
  • Filing status
  • State tax rate (approx)
  • Prior-year total tax (for safe harbor check)
  • Federal withholding from any W-2 hybrid job (offsets quarterly obligation)

Outputs:

  • Total estimated federal tax (income + SE combined)
  • Quarterly payment (the total ÷ 4)
  • Both safe harbor paths compared, lower one highlighted
  • 4 quarterly deadlines for current tax year with weekend adjustment
  • Next upcoming deadline with days-remaining countdown

Why we built these three

The autocomplete signal was overwhelming:

  • self employed calculator tax — 9/9 Google autocomplete slots are geographic qualifiers (UK, US, NZ, Ireland, 2025, take-home). Clear transactional intent.
  • contractor calculator inside ir35 + contractor calculator outside ir35 — both among the top autocomplete for "contractor calculator" in the UK.
  • freelance tax calculator — 9/9 autocomplete slots are country + rate + deductions.

Generic "contractor calculator" tools dominated by paywalled UK contractor accountant sites. Every one of them gates the calculator behind an email. Ours doesn't.

What's in the rest of the /freelance/ hub

Beyond these three tax tools, the freelance hub now has 33 tools:

Privacy note

Every calculator runs entirely in your browser. Your income figures, filing status, contract rates — none of it leaves your device. We use URL-encoded share links (not server uploads) if you want to save or share a scenario. If you clear browser storage, your calculations are gone — which for tax-related work is the privacy trade we prefer.

Disclaimer: All three tools are estimates only. Tax law changes annually. Consult a qualified accountant (US: CPA, UK: ACCA/ACA/CTA) before filing. Nothing here constitutes tax advice.

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Originally published at https://tool.teamzlab.com?utm_source=blogger&utm_medium=article&utm_campaign=2026-05-free-freelancer-tax-calculators-us-se-tax-uk-ir35-quarterly-estimator

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