Self Assessment: paper returns due by 31 October, online returns and payment by 31 January

If you are a sole trader, a partner in a business or a landlord, your 2025 to 2026 Self Assessment tax return is on the clock. The first deadline is this week: paper returns must reach HMRC by 11:59pm on 31 October 2026.

The dates

• 31 October 2026: last day for HMRC to receive a paper return.
• 30 December 2026: last day to file online if you want any tax you owe collected through your tax code.
• 31 January 2027: last day to file online and to pay any tax owed for 2025 to 2026.

HMRC says around 12 million people are expected to file by 31 January. It marked 100 days to go on 23 October.

Paying through your tax code

If you also have PAYE income — a job alongside your business, or a company pension — you may not need to pay the bill in one go. GOV.UK says HMRC can collect it through your tax code if:

• you owe less than £3,000;
• you already pay tax through PAYE;
• you file online by 30 December (or on paper by 31 October).

You cannot pay part of a bill to bring it under £3,000.

What happens if you are late

For a late return, GOV.UK lists:

• an initial £100 penalty;
• after 3 months, £10 a day, up to a maximum of £900;
• after 6 months, a further 5% of the tax due or £300, whichever is greater;
• after 12 months, another 5% or £300, whichever is greater.

Tax paid late also brings penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest.

If you are in Making Tax Digital

HMRC says people already signed up to Making Tax Digital for Income Tax still file their 2025 to 2026 return in the usual way and pay by 31 January 2027.

Watch for scams

HMRC warns that criminals often pretend to be HMRC to steal money or personal details. Do not click links in messages you did not expect, and never share your HMRC sign-in details. Search GOV.UK for "HMRC phishing and scams" to find genuine contact details.

What to do

1. If you file on paper, post it in time to arrive by 31 October — or switch to filing online, which gives you until 31 January.
2. Gather your figures now: sales, expenses and any other income for 6 April 2025 to 5 April 2026.
3. If you cannot pay in full, check the payment plan options on GOV.UK ("If you cannot pay your tax bill on time") before the bill becomes overdue.