UK side hustle tax calculator 2026/27
Estimate the extra tax on income alongside your main job, what to set aside and when it may be due.
How the side-hustle tax estimate works
The side-hustle calculator measures the additional liability created when sole-trader profit sits above salary. It keeps workplace-pension methods separate, adds Class 4 NI and selected loan or Child Benefit charges, then shows a reserve and likely Self Assessment dates.
Rules checked
Read the checking method
What the result includes
- Incremental UK or Scottish Income Tax on side profit
- Class 4 NI, selected student loans and entered Child Benefit charge
- Trading allowance comparison, monthly reserve and payments-on-account prompt
What to have ready
- Main salary and the workplace-pension tax method
- Gross side-income receipts and allowable business costs
- Student-loan and Child Benefit details where relevant
Questions about side-hustle tax
Should the reserve be a percentage of turnover or profit?
The page shows a percentage of incoming side-hustle payments for simple cash handling, but liability is calculated from taxable profit and the person’s wider income.
When is 2026/27 side-hustle tax normally due?
A first Self Assessment registration notification is generally due by 5 October 2027, with online filing and payment by 31 January 2028. Payments on account can add instalments for the following year.
Built around the current HMRC rules
Uses 2026/27 Income Tax bands, pension thresholds, the £1,000 trading allowance, Class 4 National Insurance, High Income Child Benefit Charge and current student-loan thresholds. The trading allowance is shared across relevant trades. Figures are rounded estimates, not tax advice.