Side hustle tax UK: the complete guide

A side hustle is treated by HMRC as self-employment (or, for some passive income, as miscellaneous income) regardless of whether you also have a full-time job, are a student, or run another business. Tax rules do not care how you describe the activity — they care whether it generates trading or other taxable income.

The starting point for most side hustlers is the £1,000 trading allowance, a tax-free amount of gross trading income each tax year. If your side hustle brings in £1,000 or less in gross income, you generally do not need to register with HMRC or pay tax on it at all.

Once gross income exceeds £1,000, the position changes: you must register for Self Assessment by 5 October following the end of the tax year in which the trading started, and declare the whole amount, not just the excess over £1,000.

You then choose between deducting the flat £1,000 trading allowance, or your actual allowable expenses, whichever gives the lower taxable profit — you cannot use both for the same trade.

Crucially, your side hustle profit is not taxed in isolation. It is added to any other income you have — most commonly employment income taxed through PAYE — and the combined total determines your overall Income Tax band: 20% basic rate, 40% higher rate or 45% additional rate on the top slice of income.

On top of Income Tax, side hustle profit is also subject to Class 4 National Insurance at 6% on profits between £12,570 and £50,270, and 2% above that, calculated on your self-employed profit specifically, not your combined income.

For employed side hustlers, this often means your side income is taxed at your marginal rate rather than starting again at 0% — a common surprise for people expecting a fresh personal allowance for their side hustle. There is only one personal allowance per person, shared across all income sources.

Registering does not necessarily mean owing a lot of tax. Genuine allowable expenses — equipment, software, a share of home costs, materials, platform fees — reduce your taxable profit, and small side hustles with modest turnover can end up with only a small tax bill even after registering.

If your side hustle involves selling goods or providing services through a digital platform (Etsy, eBay, Vinted, Fiverr, content platforms), be aware that platforms report seller data to HMRC once you pass reporting thresholds — but this is a separate rule from the £1,000 trading allowance and does not change your actual tax position, only HMRC's visibility of it.

As a side hustle grows, it is worth reviewing your setup periodically: whether payments on account will apply once your tax bill passes £1,000, whether Making Tax Digital for Income Tax will eventually apply as your combined income grows, and, much further down the line, whether a limited company structure would suit better.

Source: Income Tax rates and allowances (gov.uk) · Self Assessment (gov.uk)