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Self-Assessment Tax Estimator

Side hustle or self-employed? Estimate the tax and Class 4 NI you’ll owe before filing.

2026/27 tax year · for the SA return

Deductions

How this is worked out

Taxable SE profit = gross self-employed income minus allowable expenses or the £1,000 trading allowance (whichever is bigger — you can’t claim both).

Income tax is applied to your total income (PAYE + SE profit) using 2026/27 bands. The amount your employer already deducted under PAYE is credited against this — what’s left is the SA bill.

Class 4 NI is the self-employed version of NI: 6% on SE profits between £12,570 and £50,270, then 2% above. Class 2 NI was abolished from April 2024 for most.

This estimator doesn’t cover: dividends, rental income, capital gains, the High Income Child Benefit Charge, pension tax relief on relief-at-source contributions, or marriage allowance transfers. For those, the SA return itself walks you through it.

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Educational only. Not personal financial advice. Tax-year figures may change; check periodically.

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Tax year 2026/27 · Last reviewed 23 May 2026 · Educational only, not personal financial advice