This guide sets out every date that leads up to the January deadline, in the order they'll actually hit your business: registration, paper filing, and payments on account.
What Is the Self-Assessment Deadline for 2027?
If you're filing online, the deadline is 31 January 2027 at 11:59pm, covering income earned in the 2025–26 tax year (6 April 2025 to 5 April 2026). This is also when any tax owed for that year is due, along with your first payment on account for 2026–27 if applicable. If you're filing a paper return instead, that deadline moves much earlier — the paper filing deadline for the 2025/26 tax year is 31 October 2026. Given how much earlier that is, most sole traders find it's easier to file online even if they've traditionally used paper.
What Other Dates Lead Up to the Deadline?
The 31 January date gets the most attention, but four other dates matter just as much for sole traders:
| Date | What's due |
|---|---|
| 5 October 2026 | Registration deadline. If you're newly self-employed, you have until 5 October following the tax year you started trading to register for Self Assessment with HMRC. Miss this and you can still file, but you risk a penalty for late registration on top of the eventual return. |
| 31 October 2026 | Paper return deadline, with a £100 penalty applying if filed late, even if no tax is owed. |
| 30 December 2026 | PAYE coding-out deadline. If you file online by this date and owe less than £3,000, HMRC can collect the tax through your PAYE code for 2027–28 instead of as a lump sum. |
| 31 January 2027 | Online filing, balancing payment, and first payment on account for 2026–27, all due on the same date. |
| 31 July 2026 | Second payment on account toward the 2025–26 tax year, for sole traders who make payments on account. |
What Happens If You Miss the Deadline?
The penalties escalate quickly, and they apply regardless of whether you actually owe any tax. A £100 penalty applies immediately for late filing, with interest charged on unpaid tax from 1 February, and further penalties added at 3, 6 and 12 months. On top of filing penalties, a further penalty of 5% of the tax due or £300 — whichever is greater — can apply after six months of non-payment. Interest also accrues daily on any unpaid balance, so a return that's a few months late with tax still owing can end up costing considerably more than the tax bill itself.
Does Making Tax Digital Change Anything for 2027?
It's starting to, and this is worth flagging even if it doesn't apply to you yet. Making Tax Digital for Income Tax Self Assessment became mandatory from 6 April 2026 for sole traders and landlords with qualifying income over £50,000, with the threshold dropping to £30,000 from April 2027 and £20,000 from April 2028. If you're a sole trader with turnover approaching £30,000, the annual Self-Assessment return you're used to will eventually be replaced by quarterly digital updates — so it's worth getting ahead of this before it becomes compulsory for you.
How Do I Avoid Missing the Deadline?
- Register for Self Assessment as soon as you start trading, not close to the 5 October deadline.
- Keep digital records of income and expenses throughout the year rather than reconstructing them in January.
- Set aside money for payments on account so the July and January due dates don't come as a surprise.
- File a few weeks before 31 January — HMRC's system slows down in the final days, and it gives you a buffer if anything's missing.
- If you know you'll miss the deadline, contact HMRC before it passes; a reasonable excuse claim is far easier to make proactively than after a penalty has landed.
Frequently Asked Questions
The online Self-Assessment deadline for 2027 is 31 January 2027, covering income earned in the 2025–26 tax year. The paper filing deadline is earlier, on 31 October 2026.
An immediate £100 penalty applies for late filing, even if you owe no tax, with further penalties and daily interest added the longer the return remains outstanding.
No. You only need to register once when you first become self-employed, by 5 October following the tax year you started trading. After that, you file annually without registering again.
Not yet for most sole traders, but it will over the next few years. MTD for Income Tax became mandatory in April 2026 for those earning over £50,000, with the threshold falling to £30,000 in 2027 and £20,000 in 2028, eventually replacing the annual return with quarterly digital updates.
Never miss a date again. If you'd rather hand the filing itself to someone else, our Sole Traders & Self-Employed service covers registration, bookkeeping and Self Assessment filing so none of these dates catch you off guard.
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