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Head-to-head · Tax Calculators

Federal Income Tax Calculator by SmartAsset vs GOV.UK Self Assessment Tax Calculator

  • Updated Oct 2026
  • Both researched from official sources
  • 1 check side by side
Higher score Federal Income Tax Calculator by SmartAsset #1 in Tax Calculators 9.3/10 Free plan Free plan Visit SmartAsset
GOV.UK Self Assessment Tax Calculator #5 in Tax Calculators 8.5/10 Free plan Free plan Visit GOV.UK

Federal Income Tax Calculator by SmartAsset leads on 0 checks, GOV.UK Self Assessment Tax Calculator on 0, and 1 is even. Who comes out ahead on the 1 yes/no, price and count check where we have data for both products. The editor score weighs everything else too.

Our verdict

  • Highest scoreFederal Income Tax Calculator by SmartAsset · 9.3/10
  • Free planboth

Federal Income Tax Calculator by SmartAsset scores higher on our rubric for tax calculators: 9.3 against 8.5 out of 10; our editors rank them #1 and #5.

On tax jurisdictions, Federal Income Tax Calculator by SmartAsset gives you Multiple where GOV.UK Self Assessment Tax Calculator offers Federal.

Federal Income Tax Calculator by SmartAsset is the better fit for U.S. taxpayers comparing take-home pay and tax. GOV.UK Self Assessment Tax Calculator is the better fit for UK self-employed people with mixed income.

  • Federal Income Tax Calculator by SmartAsset fits best

    U.S. taxpayers comparing take-home pay and tax

  • GOV.UK Self Assessment Tax Calculator fits best

    UK self-employed people with mixed income

Advertiser disclosure: iTechGuides is reader-supported. Vendors can pay for top positions in our rankings and for a place on other products' pages, and we may earn a commission when you click some links. How we rank.

Side by side

Feature Federal Income Tax Calculator by SmartAsset 9.3/10 Visit ↗ GOV.UK Self Assessment Tax Calculator 8.5/10 Visit ↗
At a glance
Editor score 9.3 8.5
Ranking #1 in Tax Calculators #5 in Tax Calculators
Best for U.S. taxpayers comparing take-home pay and tax UK self-employed people with mixed income
Pricing model Free Free
Starting price Free plan Free plan
Free plan ✓ ✓
Free trial — —
Deployment Cloud Cloud
Platforms Web Web
Support Email Docs
Built for Solo Solo
Specs
Calculator types Federal, FICA, state and local income tax; take-home pay Income Tax; Class 4 National Insurance
Tax jurisdictions Multiple Federal
Income sources Household income; retirement account contributions and other pre-tax deductions self-employment profits; property rental income; State or occupational pension; paid employment
Filing statuses Single; married filing jointly; married filing separately; head of household Not checked yet
Tax years 2025 2025 to 2026
Platforms Web web
Our review
Pros
  • Estimates federal, FICA, state and local income taxes
  • Supports filing status, deduction, retirement and credit inputs
  • Shows marginal and effective tax rates alongside annual take-home pay
  • Estimates Income Tax for the 2025 to 2026 tax year
  • Includes Class 4 National Insurance for self-employed users
  • Combines self-employment, rental, pension, and employment income
Cons
  • Provides estimates rather than tax-return filing
  • Results may differ from actual tax outcomes
  • Available on the web rather than as a listed native app
  • Assumes the standard Personal Allowance
  • Does not account for savings and investment income
  • Excludes the High Income Child Benefit Charge and amounts already paid
Our verdict

SmartAsset’s Federal Income Tax Calculator is a free web tool for people estimating taxes and take-home pay. It accepts household income, location and filing status, with choices for single, married filing jointly, married filing…

Read the review →

GOV.UK’s Self Assessment Tax Calculator is a free web tool from HM Revenue & Customs for estimating Income Tax for the 2025 to 2026 tax year. For self-employed users, it also estimates Class 4 National Insurance. It is aimed at people who…

Read the review →
  1. Federal Income Tax Calculator by SmartAssetTax Calculators 9.3Free plan
  2. GOV.UK Self Assessment Tax CalculatorTax Calculators 8.5Free plan

Strengths and trade-offs

  • Federal Income Tax Calculator by SmartAsset — where it wins

    • Estimates federal, FICA, state and local income taxes
    • Supports filing status, deduction, retirement and credit inputs
    • Shows marginal and effective tax rates alongside annual take-home pay

    Where it doesn't

    • Provides estimates rather than tax-return filing
    • Results may differ from actual tax outcomes
    • Available on the web rather than as a listed native app

  • GOV.UK Self Assessment Tax Calculator — where it wins

    • Estimates Income Tax for the 2025 to 2026 tax year
    • Includes Class 4 National Insurance for self-employed users
    • Combines self-employment, rental, pension, and employment income

    Where it doesn't

    • Assumes the standard Personal Allowance
    • Does not account for savings and investment income
    • Excludes the High Income Child Benefit Charge and amounts already paid
  • Federal Income Tax Calculator by SmartAsset9.3/10 · Free plan

    A free web calculator for comparing estimated taxes and take-home pay.

    Visit SmartAssetFull verdict →
  • GOV.UK Self Assessment Tax Calculator8.5/10 · Free plan

    A free web calculator for estimating 2025–26 tax across several income sources.

    Visit GOV.UKFull verdict →

More comparisons

All tax calculators comparisons → · Full ranking →

Guides on tax calculators

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

Last updated · How we research and update