Home / Tax on side hustle income: a practical guide
Income from freelance work, selling goods or services, or any other self-employment activity is generally taxable. If you also have employment income, the two sources interact — your personal allowance and tax bands are shared — which affects both the marginal rate on your side income and how much you need to set aside.
HMRC allows a £1,000 trading allowance each tax year. If your total gross income from self-employment (before any expenses) is £1,000 or less, you do not pay tax on it, do not need to register as self-employed, and do not need to file a Self Assessment return on the basis of that income alone.
If gross income exceeds £1,000, you must register as self-employed with HMRC, file a Self Assessment return and pay tax on any taxable profit above your overall tax-free amount. You cannot claim both the trading allowance and actual business expenses in the same calculation — you use whichever produces the better result.
For modest occasional income, the trading allowance provides a clean answer. Once income grows, Self Assessment obligations begin and need to be managed proactively.
If you have both PAYE employment income and self-employed side income, your tax position differs from someone purely self-employed. The Personal Allowance and basic rate band are shared across all sources: employment earnings are typically counted first, and self-employed profit sits on top.
This means that if your employment income already consumes your personal allowance and fills the basic rate band, your self-employed profit could be taxed at 40% — even if the self-employed income itself is modest. A freelancer employed full-time at £45,000 and earning an additional £10,000 from freelance work will pay 40% income tax on that £10,000 (plus 6% Class 4 NI above the lower profits limit), not 20%.
Use the other income field in this calculator to enter your employed gross salary. The estimate will then calculate tax on your self-employed profit at the correct marginal rate. Without this, the calculator assumes all income starts from zero, which will understate your actual tax exposure.
Class 4 NI applies to self-employed profit above £12,570 regardless of whether the self-employment is full-time or a side income. At 6% on profits between £12,570 and £50,270, the Class 4 charge adds meaningfully to the effective rate on self-employed income.
If you are employed and earning above the NI primary threshold through PAYE, there is a maximum combined NI contribution limit. It is theoretically possible to have overpaid NI where employment and self-employment NI together exceed the annual maximum. HMRC handles this through Self Assessment but the interaction is not modelled in this calculator — check with HMRC or an accountant if this may apply.
If side income exceeds £1,000 gross in a tax year, register as self-employed with HMRC by 5 October following the end of that tax year. For income earned in 2026/27 (ending 5 April 2027), the registration deadline is 5 October 2027.
Once registered, you file a Self Assessment return covering both employment and self-employed income. PAYE employment income is pre-populated from employer data; you add your self-employed profit and expenses. Tax already paid through PAYE is taken into account and the return shows any remaining balance.
Keeping separate records of side-hustle income and expenses from the start — even a basic spreadsheet of invoices and costs — makes the return straightforward to complete and reduces the risk of missing allowable expenses.
The homepage calculator is the fastest way to turn this guidance into a concrete monthly take-home and tax reserve estimate.
If gross side income is £1,000 or less, the trading allowance applies and registration is not required. If it exceeds £1,000, you must register as self-employed and file a Self Assessment return.
Enter your gross employment salary in the other income field. The calculator will then estimate tax on your self-employed profit at the correct marginal rate, accounting for personal allowance and rate band already used by your employment income.
Class 4 NI at 6% applies to self-employed profit above £12,570. There is an annual maximum combined NI amount where employment and self-employment NI overlap — check with HMRC if this may apply to your situation.
Yes, if the costs are wholly and exclusively for the self-employed activity. The usual allowable expense rules apply. If your gross side income is only just above £1,000 and actual expenses are less than £1,000, using the trading allowance rather than actual expenses may be simpler.