Self Assessment
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Who has to file a UK Self Assessment return, the key deadlines and penalties, payments on account, the £1,000 trading allowance and side-hustle reporting — sourced directly from HMRC.
- Self Assessment
Filing Self Assessment: deadlines, penalties and how to submit
HMRC require a Self Assessment return where someone is self-employed and earned over £1,000 in trading income, is a partner in a partnership, has untaxed income over £2,500, has rental income over £2,500 (or gross rents over £10,000), has total income over £150,000, has Capital Gains above the annual exempt amount, has to pay the High Income Child Benefit Charge, or has been told by HMRC to file. The HMRC online checker at gov.uk/check-if-you-need-tax-return is definitive.
- Self Assessment
Self Assessment deadlines and penalties 2025/26
For 2025/26 income, paper returns are due 31 October 2026 and online returns 31 January 2027 — also the payment deadline. HMRC charge an automatic £100 penalty for missing the filing deadline (even with nothing owed), then £10/day after 3 months (up to £900), 5% of tax owed at 6 months, and another 5% at 12 months. Late-paid tax also attracts interest, set at Bank Rate + 4 percentage points from April 2025.
- Self Assessment
Self Assessment payments on account explained
Payments on account are two advance instalments towards next year's Self Assessment bill, each equal to half of last year's tax. They're due on 31 January and 31 July. HMRC require payments on account when the previous year's Self Assessment bill was over £1,000 and less than 80% of all tax was collected at source (e.g. through PAYE).
- Self Assessment
The £1,000 trading allowance and side-hustle tax
The trading allowance lets UK residents earn up to £1,000 of gross trading or miscellaneous income each tax year without telling HMRC. Above £1,000, a Self Assessment return is required and the £1,000 can be claimed as an alternative to actual expenses. A separate £1,000 property allowance works the same way for rental income.