Self Assessment / side-hustle tax calculator

Because the £12,570 personal allowance and the tax bands apply to your total income across every source combined, not per source. If your job already earns £35,000, your job has already used £22,430 of the basic-rate band — so your next pound, whether it comes from a payrise or a side hustle, is taxed at 20% (or higher once you pass £50,270 combined), not from a fresh 0% allowance.

The trading allowance lets you deduct up to £1,000 from your gross side-hustle income with no receipts needed, instead of claiming your real business expenses — but it's one or the other, not both. Use whichever is larger: if your actual expenses are under £1,000, the trading allowance gives a bigger deduction (and less paperwork); if they're higher, claim the real expenses instead. This calculator flags which one would help more.

This is the classic Self Assessment surprise. Once your bill goes over £1,000, HMRC doesn't just collect what you owe for the year just gone — it also asks for 50% of that amount again, twice (31 January and 31 July), as an advance toward the year ahead. So your very first payment can be 1.5× your actual tax bill for that year. It evens out in later years (each January payment nets off against what you actually end up owing), but it genuinely catches first-timers out.

If your gross side-hustle/self-employment income for the tax year is £1,000 or less, no — the trading allowance covers it automatically and there's nothing to declare (assuming you have no other reason to file). Above £1,000, you need to register with HMRC by 5 October following the end of the tax year the income started in, then file and pay by the following 31 January.

Class 2 is now effectively abolished for most self-employed people — if your profits are above the Small Profits Threshold (roughly £7,105), you're automatically treated as having paid it, protecting your State Pension record, with nothing to actually pay. Below that threshold, paying it voluntarily (a small flat weekly amount) is optional, purely to keep building your State Pension entitlement — not modelled in this calculator since it's optional and separate from the tax bill itself.

It's based on where you live (your main residence), not where your work or clients are based. If you live in Scotland, select Scotland — it applies Scotland's own Income Tax bands to your combined income.

Add up the gross income from all of them together — the £1,000 trading allowance is a single annual allowance across all your self-employment/casual income combined, not one per business or platform.

It's HMRC's move away from one annual Self Assessment return towards digital record-keeping and quarterly updates, phased in by gross qualifying income (your turnover before expenses, combining self-employment and property income) — above £50,000 from 6 April 2026, above £30,000 from 6 April 2027, and above £20,000 from 6 April 2028. It doesn't change how much tax you owe, only how and how often you report it, and you'll need MTD-compatible software once you're in scope.

No — treat it as a planning estimate, not a tax return. It assumes a standard tax code on your employment income and doesn't account for things like pension contributions, Gift Aid, other income sources, or the 80%-collected-at-source exemption from payments on account. Always confirm final figures with an accountant, HMRC's own tools, or your Self Assessment software before filing.