Quick answer
The deadline for a paper Self Assessment return is 31 October after the tax year ends, three months earlier than the 31 January online deadline. Missing it means you must file online instead, or risk penalties.
Updated October 2026 · Figures based on 2026/27 rates
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Paper vs online deadlines
Paper returns must reach HMRC by 31 October following the end of the tax year on 5 April. Online returns can be filed until 31 January. Payment of any tax due is always 31 January, whichever way you file.
Who still files on paper?
Most people now file online, but paper is still used by some trustees, those without internet access and certain special cases such as some non-resident forms. You must request the paper SA100 and supplementary pages from HMRC or download and print them.
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What happens if you miss 31 October?
You can still file online by 31 January without a late filing penalty. If you file on paper after 31 October, the £100 late filing penalty can apply once the 31 January deadline passes, so switching to online is usually the safest route.
Why most people choose online
Online filing gives you instant confirmation, built-in checks and an extra three months. HMRC also calculates the tax for you straight away, which makes it easier to plan your payment.
Paper or online: how the two deadlines compare
Self Assessment has two filing deadlines for the same return. A paper return must reach HMRC by 31 October after the end of the tax year. An online return can be filed up to 31 January, three months later. Whichever route you choose, any tax you owe is normally due by 31 January, so choosing paper does not give you an earlier payment date. For most people, filing online is easier, gives a faster confirmation and leaves more time, which is why the great majority choose it.
| Item | Paper return | Online return |
|---|---|---|
| Filing deadline | 31 October | 31 January |
| Payment deadline | 31 January | 31 January |
| Second payment on account | 31 July | 31 July |
| Proof of filing | Your own proof of posting | Instant online confirmation |
Paper filing can still be appropriate if you cannot file online, for example because of a specific circumstance HMRC has accepted. You need to obtain the form and any supplementary pages for your income, complete them accurately and post them in good time. Keep proof of posting and a copy of everything.
A worked example of what a missed deadline can cost
This is an illustrative example, not a real taxpayer. Leo is a self-employed tradesman who intended to file online but did not file until 15 September, about seven and a half months after the 31 January deadline. His tax bill for the year was £4,000, which he also did not pay until 15 September.
| Charge | Working | Amount |
|---|---|---|
| Initial late filing penalty | One day late | £100 |
| Daily penalties | £10 a day for up to 90 days, after the 3-month point | £900 |
| 6-month filing penalty | Greater of 5% of £4,000 (£200) or £300 | £300 |
| Late payment, 30 days | £4,000 x 5% | £200 |
| Late payment, 6 months | £4,000 x 5% | £200 |
| Total penalties | £100 + £900 + £300 + £200 + £200 | £1,700 |
Interest at Bank Rate + 4% on the unpaid tax is charged on top. If Leo had a reasonable excuse, he could appeal, but ordinary pressure of work usually does not count. Filing online on time would have cost him nothing extra beyond the tax itself.
What to do if you have missed the paper deadline
Missing 31 October only matters if you intend to file on paper. Switching to online filing gives you until 31 January, so many people who have missed the paper date simply file online. You will need your UTR and an activated Government Gateway account. If you still need to register, remember that the registration deadline is 5 October after the tax year ends, so a late registration may bring its own problems.
Common mistakes
- Thinking that a paper return buys more time to pay. The payment deadline remains 31 January.
- Posting at the last minute with no proof of posting.
- Using the wrong tax year’s form or leaving out supplementary pages.
- Believing that a 31 October deadline applies to online filers. It does not.
- Waiting for the activation code until January, then missing the deadline.
A short checklist
- Decide whether you need paper or can file online.
- Check that your UTR and Government Gateway account are active.
- Gather your records and complete the figures for the right year.
- Submit, keep proof, and diarise 31 January for payment.
Related reading
Read the 31 January Self Assessment deadline guide, late payment penalties, reasonable excuses for late returns and what happens if you miss the deadline. If you are already late, see our late Self Assessment tax return service.
SATR can prepare and file your return online for a fixed fee from £199 + VAT, using qualified UK accountants, so you do not need to worry about paper deadlines.
This is general information, not personal tax advice.
Why many people now choose to file early online
Filing well before the deadline has practical benefits. You see your tax calculation sooner, so you know what to pay and can budget for it. You have time to fix problems such as a missing activation code or a forgotten source of income. And if you are due a refund, you may receive it sooner. If your records are ready in the spring after the tax year ends, there is no reason to wait until January. Remember that filing early does not bring the payment date forward, so you can still pay on 31 January.
Frequently asked questions
Can I submit a paper return after 31 October?
You can, but it will be treated as late for the 31 October paper deadline and you would need to rely on the later online deadline to avoid penalties.
Is the payment deadline also 31 October?
No. Any tax due is payable by 31 January for both paper and online returns.
Tax rules and rates change. Figures here reflect 2026/27 guidance; always check current HMRC rules or ask us before acting.
Can I still file online after 31 October?
Yes. The 31 October date is only for paper returns. Online returns can be filed until 31 January after the end of the tax year.
Does a paper return change when I pay?
No. Any tax due is normally payable by 31 January however you file.
How do I prove my paper return was posted?
Use a method that gives proof of posting and keep a copy of the return. HMRC may ask for evidence if the return is disputed.
Related guides
- Self Assessment Deadline 31 January 2027: Preparation Plan
- What to Do If HMRC Opens an Enquiry Into Your Tax Return
- How to Claim a Self Assessment Tax Refund
- late Self Assessment service
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The Bottom Line
The 31 October deadline only applies to paper returns. With online filing giving you until 31 January, instant confirmation and the tax calculated for you, paper is rarely the better option. If you have missed 31 October, do not post a paper return and hope — simply file online instead.
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