Missing a Self Assessment deadline in the UK triggers an automatic £100 penalty from HMRC — even if you don't owe any tax at all. Between registration deadlines, paper vs. online filing dates, the balancing payment, and payments on account, it's easy to lose track of which date applies to which tax year. This guide lays out every Self Assessment deadline relevant right now, plus the full 2026/27 tax year calendar, so nothing catches you off guard.
UK Self Assessment Deadline 2026/27 – Full Guide
📑 Table of Contents
🎯 The Deadline You Likely Need Right Now: 31 January 2027
| Deadline | Date | What's Due |
|---|---|---|
| Registration | 5 October 2026 | Register with HMRC if newly self-employed or with untaxed income in 2025/26 |
| Paper return | 31 October 2026 | Submit a paper Self Assessment return for 2025/26 |
| Online return + balancing payment | 31 January 2027 | File online, pay any balance owed for 2025/26, plus first payment on account for 2026/27 |
| Second payment on account | 31 July 2027 | Second advance instalment toward your 2026/27 tax bill |
This is the deadline set that applies to nearly everyone reading this in 2026 — it covers income earned during the 2025/26 tax year (6 April 2025 to 5 April 2026).
📅 Full 2026/27 Tax Year Calendar
For income you earn during the 2026/27 tax year (6 April 2026 – 5 April 2027), here's when that return will actually be due:
| Deadline | Date | What's Due |
|---|---|---|
| Tax year starts | 6 April 2026 | Start of the 2026/27 tax year |
| Registration | 5 October 2027 | Register with HMRC if newly self-employed or with untaxed income in 2026/27 |
| Tax year ends | 5 April 2027 | End of the 2026/27 tax year |
| Paper return | 31 October 2027 | Submit a paper Self Assessment return for 2026/27 |
| Online return + balancing payment | 31 January 2028 | File online, pay any balance owed for 2026/27, plus first payment on account for 2027/28 |
| Second payment on account | 31 July 2028 | Second advance instalment toward your 2027/28 tax bill |
📝 Registering for Self Assessment
If you became self-employed, started renting out property, or had other untaxed income for the first time during a tax year, you must register with HMRC by 5 October following the end of that tax year. Registering gives HMRC time to issue your UTR (Unique Taxpayer Reference) and activate your online account — this process can take several weeks, so registering right at the deadline risks not having your UTR in time to file by January. Late registration itself doesn't carry an automatic fine, but it can trigger penalties indirectly if it causes you to file your return late as a result.
📄 Paper vs. Online Filing
HMRC gives you two ways to file, with very different deadlines:
- Paper returns: Due by 31 October — a full three months earlier than online filing.
- Online returns: Due by 31 January, giving you significantly more time to prepare.
Because of this gap, the overwhelming majority of filers choose to file online. One important 2026 change: from April 2026, self-employed individuals and landlords with total annual income over £50,000 can no longer simply file a traditional paper or online Self Assessment return — they fall under new Making Tax Digital requirements instead (more below).
💳 Payments on Account Explained
If your Self Assessment tax bill exceeds £1,000, and less than 80% of your tax was already collected at source (for example, through PAYE), HMRC requires you to make payments on account — advance instalments toward your next year's estimated tax bill. Each instalment is 50% of your previous year's tax bill.
This catches many first-time filers off guard — the January bill is often much larger than expected because it bundles the prior year's balance with next year's advance payment. If you expect your income to drop, you can apply to reduce your payments on account using form SA303 through your HMRC online account — but if you reduce them too much and end up owing more later, HMRC charges interest on the shortfall.
⚠️ Penalties for Missing a Deadline
| How Late | Penalty |
|---|---|
| 1 day late | £100 automatic penalty (even if no tax is owed) |
| 3 months late | £10/day, up to a 90-day maximum of £900 (on top of the £100) |
| 6 months late | Additional £300 or 5% of tax owed, whichever is higher |
| 12 months late | A further £300 or 5% of tax owed (potentially higher in serious cases) |
On top of filing penalties, separate interest charges apply to any unpaid tax from 1 February onward, calculated daily until paid in full — filing late and paying late are penalized independently of each other.
💻 Making Tax Digital (MTD) for ITSA
Making Tax Digital for Income Tax Self Assessment is now live, starting 6 April 2026, for self-employed individuals and landlords with total qualifying income over £50,000. Those in scope must use HMRC-approved software to keep digital records and submit four quarterly updates throughout the year, followed by a final year-end declaration that replaces the traditional annual Self Assessment return. HMRC has confirmed plans to extend MTD to those earning over £30,000 in a future phase — worth watching if you're close to that threshold.
❓ Frequently Asked Questions
It depends what you mean: the tax return covering income earned during the 2025/26 tax year (which most people need to file during 2026) is due 31 January 2027. The return covering the 2026/27 tax year itself (6 April 2026 to 5 April 2027) isn't due until 31 January 2028.
An automatic £100 penalty applies immediately, even if you owe no tax. Further penalties build at 3, 6, and 12 months late, plus daily interest on any unpaid tax starting 1 February.
Advance instalments toward next year's estimated tax bill, required if your Self Assessment bill exceeds £1,000 and less than 80% of your tax was collected at source. Each instalment is 50% of the previous year's tax bill, due 31 January and 31 July.
No, only once when you first become liable — for example, when you start self-employment or receive new untaxed income. After that, HMRC continues sending you a return to file each year until you formally deregister.
A new HMRC requirement, live from 6 April 2026, for self-employed individuals and landlords earning over £50,000. It requires HMRC-approved software for digital record-keeping and four quarterly updates, replacing the traditional annual paper/online Self Assessment return.
Yes, if you expect lower income in the coming year, you can apply to reduce payments on account using form SA303 via your HMRC online account. Over-reducing them, however, means HMRC will charge interest on any resulting shortfall.
See your Class 1, 2, or 4 NI alongside your Self Assessment bill.
Try the UK National Insurance Calculator →
📚 References
This article is compiled from official HMRC guidance and leading UK tax publications, current as of publication:
- GOV.UK — Self Assessment Tax Returns: Deadlines
- GOV.UK — Understanding Payments on Account
- GOV.UK — Making Tax Digital for Income Tax
- QuinetCalc UK National Insurance Calculator
This article is for general informational purposes only and does not constitute tax or legal advice. Deadlines and penalty rules are set by HMRC and may be updated — always verify current dates on GOV.UK or consult a licensed accountant before filing.
Post a Comment
0Comments