Self Assessment Tax Deadlines: When to register, file and pay

Team Nomi

Jul 15, 2026
6 minutes read

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The deadline for filing your Self Assessment tax return is 31 January, but there are several other important Self Assessment deadlines throughout the year that you should not overlook. 

From registering with HMRC and submitting paper returns to paying your tax bill and managing payments on account, each date plays an important role in staying compliant. Missing a deadline could lead to penalties, interest charges, and unnecessary stress. 

Whether you are self-employed, a landlord, freelancer, or have other untaxed income, understanding these dates can help you plan ahead and avoid last-minute issues. In this blog, we cover all the important Self Assessment tax deadlines for the 2026-27 tax year and explain what each one means.

Self Assessment Tax deadlines

The UK tax year runs from 6 April to 5 April. For the 2026-27 tax year (6 April 2026 to 5 April 2027), these are the important deadlines.

Deadline to register for Self Assessment – 5 October

One of the most important dates to remember is the deadline to register for self assessment.

If you need to complete a Self Assessment tax return and have not registered before, you must tell HMRC by 5 October following the end of the tax year. For income earned during the 2026-27 tax year, the registration deadline is 5 October 2027.

Registering early gives you enough time to receive your Unique Taxpayer Reference (UTR) and access HMRC services before filing.

Paper tax return deadline – 31 October

If you submit your Self Assessment using paper forms, HMRC must receive your return on 31 October following the end of the relevant tax year.

Paper filing gives less time than online filing.

Paper filing may suit:

• • People with simple tax situations
  • Individuals who prefer manual filing
  • Cases where online submission is unavailable

However, most taxpayers now choose online filing because it offers more time and convenience.

Online Self Assessment deadline – 31 January

The most commonly used filing method is online submission.

For the 2026-27 tax year, your online return must be submitted by 11:59 pm on 31 January 2028.

This deadline applies whether you prepare the return yourself or use an accountant.

Before submitting, prepare:

• • UTR number
  • National Insurance number
  • Income records
  • Expense receipts
  • Bank statements
  • Pension contribution details
  • Investment or rental income records

Submitting early can also help you understand your tax bill sooner.

Deadline to pay your Self Assessment Tax – 31 January

Submitting your tax return is only part of the process.

You must also pay any tax owed by 31 January 2027.

Late payment may result in:

• • Interest charges
  • Additional penalties
  • Collection action by HMRC

Many people file early but leave payment until the deadline date.

Deadline to pay through your tax code – 30 December

If eligible, you may ask HMRC to collect your Self Assessment bill through your PAYE tax code.

To use this option, your online return must be submitted by 30 December 2027.

If you miss this date, you can still submit online until 31 January but will need to pay another way.

Payment on account deadline – 31 July

Some taxpayers make advance tax payments called payments on account.

These are usually made in two instalments:

Payments on account help spread tax payments across the year.

What happens in late registration for Self Assessment?

Late registration for self assessment can create problems if HMRC believes you should have registered earlier.

If you register after 5 October, HMRC may issue a different filing deadline, usually three months from the date of their letter or email. However, the tax payment deadline may still remain unchanged.

Possible consequences include:

• • Penalties
  • Interest on unpaid tax
  • Delays receiving login details
  • Last-minute filing stress

If you realise you missed the registration date, it is usually better to act quickly rather than delay further.

Avoid missing Self Assessment deadlines with the right software

If you are an accountant or business owner, keeping track of Self Assessment tax deadlines can sometimes become difficult, especially during busy periods. Missing a filing or payment date can lead to penalties, interest charges, and unnecessary stress. In many cases, people simply forget their Self Assessment deadlines or leave tax filing until the last minute.

Using the right software can make the process much easier.

Nomi’s Self Assessment tax return software helps you manage and submit returns quickly and efficiently. It helps keep your tax information organised, reduces manual work, and supports timely submissions to HMRC. Instead of worrying about important dates or complex calculations, you can complete your tax return in minutes.

Experience the benefits firsthand with a 30 day free trial and its features and functionalities. Self assessment software pricing is transparent and competitive, ensuring value for your investment.

Frequently Asked questions

1. Do you have to pay Self Assessment tax by 31st January?
   Ans: If you owe tax through Self Assessment, you usually need to pay it by 31 January following the end of the tax year. This is also the deadline for submitting your online tax return. Paying late may result in interest charges and penalties from HMRC.

2. What happens if I don’t do my tax return by October 31?
   Ans: If you miss 31 October, you can no longer submit a paper tax return for that tax year. However, you may still be able to file online until 31 January. If you miss the final filing deadline, HMRC may charge penalties.

3. What happens if I miss my HMRC deadline?
   Ans: If you miss an HMRC deadline, you may face penalties and interest charges depending on whether the delay relates to registration, filing, or payment. The longer the delay continues, the more charges may apply.

4. How much does HMRC fine you for a late tax return?
   Ans: HMRC normally charges an initial £100 penalty if your tax return is late, even if you have no tax to pay. Additional penalties and interest may apply if the return remains outstanding or tax payments are delayed.