The Self Assessment dates that actually matter

Tax has a handful of deadlines, and missing one costs money. The good news: there are only four dates to know, and they're the same every year. Here they are, in plain English.

The UK tax year runs from 6 April to 5 April. Everything below refers to the tax year that has just ended — so for the year ending 5 April 2026, these are the dates that follow it.

The four dates to remember

• 5 October — the deadline to register for Self Assessment if you've never filed before. Tell HMRC you have income to declare, and they'll set you up.
• 31 October — the deadline if you file a paper return. Almost nobody needs to; online gives you three more months.
• 31 January — the big one. Your online return is due, and any tax you owe must be paid by this date too.
• 31 July — if you make payments on account, your second instalment is due.

Don't leave registering to the last minute

Registering isn't instant. HMRC posts you a Unique Taxpayer Reference (UTR), and that can take a couple of weeks to arrive — longer in busy periods. If you only realise in January that you should have registered in October, you can be left scrambling. If in doubt, register early; there's no harm in it.

What Making Tax Digital changes

From April 2026, Making Tax Digital for Income Tax starts replacing the single annual return with quarterly updates for those above the income thresholds. If that's you, the rhythm of deadlines changes — more often, but smaller each time. We keep track of all of them for you either way.

Related guides

• How to register with HMRC — the very first deadline
• Missed the deadline? — what happens next
• How much tax will I pay? — before it's due

This guide is general information, not personal tax advice. Deadlines and rules can change — always confirm the current position on GOV.UK or ask us to check. Figures reflect the 2025/26–2026/27 position.