Answers · UK 2025/26
What is the deadline to register for Self Assessment?
You must register for Self Assessment by 5 October following the end of the tax year in which you first need to file. For the 2025/26 tax year (ending 5 April 2026), the registration deadline is 5 October 2026. Late registration can result in a penalty of up to £100.
Full answer
**Self Assessment registration** is required whenever you have taxable income or gains that are not fully collected through PAYE. The registration deadline is **5 October** following the end of the relevant tax year. **Why you must register for Self Assessment:** - Self-employment income (gross income over £1,000 trading allowance) - Property rental income (gross over £1,000) - Income over £100,000 (Personal Allowance taper, regardless of PAYE) - Untaxed income over £2,500 - Capital gains above the CGT allowance (£3,000 in 2026/27) - Child Benefit and a partner earns over £60,000 (High Income Child Benefit Charge) - Foreign income - Director of a limited company receiving untaxed income - Trustee or executor with tax to declare **Registration deadlines:** | Tax year | Register by | |---|---| | 2024/25 (ended 5 Apr 2025) | **5 October 2025** | | 2025/26 (ended 5 Apr 2026) | **5 October 2026** | | 2026/27 (ends 5 Apr 2027) | **5 October 2027** | **How to register:** 1. Visit **gov.uk/register-for-self-assessment** 2. Complete the online registration form (takes ~15 minutes) 3. HMRC posts your **Unique Taxpayer Reference (UTR)** — allow **10 working days** (21 days if abroad) 4. Then activate your HMRC online account — allow another **7 working days** for the activation code 5. **Start early** — the UTR + activation process can take 4–5 weeks total **Late registration penalty:** Missing the 5 October deadline can result in a **penalty up to £100**, plus interest on any tax paid late. **Filing and payment deadlines (after registering):** - Paper return: 31 October - Online return: **31 January** following the tax year - Payment: **31 January** (with a second payment on account by **31 July**)
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This answer is informational only and does not constitute financial, tax or legal advice. Figures are for the 2025/26 UK tax year. See our methodology and sources.