Self Assessment Tax Return FAQs

Self Assessment is the system HMRC uses to collect Income Tax from people whose income is not fully taxed at source, such as the self-employed, landlords and company directors.

You usually need to file if you are self-employed with income over £1,000, a landlord, a company director, have untaxed income or gains, or earn over £100,000. See registering for Self Assessment.

For 2025/26, paper returns were due by 31 October 2026 and online returns are due by 31 January 2027, which is also the deadline to pay.

An automatic £100 penalty, then £10 a day after 3 months (up to £900), then further penalties at 6 and 12 months. See late returns.

A Unique Taxpayer Reference is the 10-digit number HMRC gives you when you register for Self Assessment.

Advance payments towards next year’s tax bill, due on 31 January and 31 July, each usually half of your previous year’s bill.

Yes. Allowable expenses reduce your taxable profit. Our accountants review every claim.

Our fixed fees start from £199 + VAT. See pricing.

At least 5 years after the 31 January filing deadline for the relevant tax year.

Yes. See penalty appeals.

SATR is a trading style of Accotax, a firm of qualified accountants based in London.