Self-Assessment Tax Estimator
Side hustle or self-employed? Estimate the tax and Class 4 NI you’ll owe before filing.
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.
Before using this estimate
2026/27 planning estimate for England, Wales and Northern Ireland, not the 2025/26 return due in January 2027. Excludes payments on account, student loans, loss relief, pensions and special NI interactions.
Check the source guidanceRelated guides
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