Self Assessment checklist: 100 days to 31 January 2027

This Self Assessment checklist covers the 100 days before the deadline for the 2025 to 2026 tax year. The online filing and payment deadline is 11:59pm on 31 January 2027, which is a Sunday. HMRC expects around 12 million people to file, so starting in November gives you time to gather records and plan the payment.

The dates that matter

If you missed the 5 October registration date and still need a return, register now. A late registration can bring a failure to notify penalty if you also do not pay in full by 31 January.

Checklist for the next 100 days

1. Check whether you need a return. HMRC’s online checker confirms this. Typical triggers are self-employment income over £1,000, rental income, partnership income or a Capital Gains Tax bill. See who needs to file a Self Assessment return.
2. Register if you are new. You need a Unique Taxpayer Reference before you can file.
3. Gather your records. Keep bank statements, invoices, receipts, pension and dividend statements and any P60. Our record keeping guide lists what to keep.
4. Add up income and costs for the year to 5 April 2026. Use the cash basis or accruals basis your accounts follow.
5. File early. Filing in November tells you the bill before January, so you can budget. It also speeds up any refund.
6. Decide how to pay. Work out the 31 January bill plus any first payment on account.
7. Use the tax code option if it suits you. Employees with PAYE income can file online by 30 December and have the tax collected through their code.
8. Take a payment plan before you are late. If you cannot pay in full, contact HMRC before 31 January.

Paying the bill on time

You pay the balancing amount and the first payment on account on 31 January. A payment on account is an advance towards the next year’s bill. If you make them, the second is due on 31 July. Read our guide to payments on account to see how they are worked out and how to reduce them.

Because 31 January 2027 is a Sunday, do not leave the payment to the last evening. Our budget payment plan guide explains how to pay in smaller amounts before the deadline.

Penalties if you are late

For a late return the penalties are:

• an initial £100 penalty
• after three months, daily penalties of £10 a day, up to a maximum of £900
• after six months, a further 5% of the tax due or £300, whichever is greater
• after 12 months, another 5% of the tax due or £300, whichever is greater

Late payment is penalised separately. You are charged 5% of the unpaid tax at 30 days, six months and 12 months, plus interest. Full detail is in our guide to HMRC penalties.

If you are in MTD for Income Tax

MTD for Income Tax does not remove the tax return for 2025 to 2026. HMRC says customers signed up to MTD still submit their Self Assessment return in the usual way and pay any tax owed by 31 January 2027. For 2026 to 2027 and later years, the return is filed through your MTD software after the quarterly updates.

If you are in the April 2026 group, make sure the 7 November quarterly update is also on your list. See the guide to the 7 November 2026 update.

Protect yourself from scams

HMRC warns that criminals impersonate it to steal money or personal details. Stop and think before sharing information in response to a call, text or email. If you are unsure whether contact is genuine, check how HMRC contacts customers on GOV.UK, or use the numbers in our HMRC telephone numbers guide.

Frequently asked questions

When is the Self Assessment deadline for 2025 to 2026?

The online filing and payment deadline is 11:59pm on 31 January 2027. The paper deadline was 31 October 2026.

What is the deadline to pay Self Assessment tax through my tax code?

You must file online by 11:59pm on 30 December 2026. If you miss that, you have to pay another way.

Do I still file a Self Assessment return if I joined MTD for Income Tax?

Yes, for 2025 to 2026. HMRC confirms MTD customers file their return in the usual way and pay by 31 January 2027.

Can I file my Self Assessment tax return early?

Yes. You can file once the tax year has ended on 5 April, and HMRC encourages early filing so you know the bill, can budget and can claim any refund sooner.