Q: What are the Self Assessment deadlines for 2026/27?

For the 2026/27 tax year (6 April 2026 – 5 April 2027), the deadlines are: register by 5 October 2027 if new, file a paper return by 31 October 2027, file online and pay any tax owed by 31 January 2028, and pay the first payment on account for 2027/28 also by 31 January 2028. The second payment on account is due 31 July 2028.

Question 1

Who needs to file a UK Self Assessment tax return?

Accepted Answer

You must file a return if you were self-employed with gross trading income over £1,000, a partner in a business partnership, received untaxed income (rental, dividends over the £500 allowance, savings interest above your allowance, foreign income), made capital gains above the £3,000 exemption, or are liable to the High Income Child Benefit Charge (income over £60,000, full withdrawal at £80,000). There is no longer a fixed employment-income threshold that forces a return — that was removed from 2024/25. The full list is on gov.uk; register by 5 October following the tax year.

Question 2

What are the Self Assessment deadlines for 2026/27?

Accepted Answer

For the 2026/27 tax year (6 April 2026 – 5 April 2027), your balancing payment plus the first payment on account for 2027/28 are both due by 31 January 2028. The second payment on account follows on 31 July 2028.

Payments on account each equal 50% of your prior year's income tax and Class 4 NI (if that came to more than £1,000 and less than 80% of your tax was collected at source). The calculator below shows the full picture so you can budget accurately.

Question 3

What are payments on account?

Accepted Answer

If your Self Assessment tax bill is over £1,000 and less than 80% is collected via PAYE, HMRC asks you to pay 50% of next year's estimated bill in January and another 50% in July. So your January 2028 bill could include your 2026/27 balance plus the first 50% of 2027/28 — easily 150% of your tax for the year. Our calculator shows this combined figure so you don't get caught out.

Question 4

What's the penalty for filing Self Assessment late?

Accepted Answer

£100 immediately on 1 February if filed late, even if no tax is owed. After 3 months, £10/day up to £900. After 6 months, an additional 5% of tax owed (minimum £300). After 12 months, another 5% (minimum £300). Tax paid late attracts interest at the Bank of England base rate plus 4 percentage points — 7.75% with the base rate at 3.75% (September 2026) — plus a 5% surcharge at 30 days, 6 months and 12 months. If you are in Making Tax Digital for Income Tax from April 2026, the new late payment regime applies instead: 3% of the unpaid tax at day 15, a further 3% at day 30, then 10% a year accruing daily from day 31.

Question 5

What expenses can I claim on Self Assessment?

Accepted Answer

Allowable business expenses include: office costs (stationery, software, business phone), travel (not commuting), staff wages, things bought to resell, business premises costs, advertising, training that updates existing skills, and a fair use-of-home charge (or £6/week simplified flat rate). You can deduct pension contributions, charity donations (Gift Aid) and trading allowance (£1,000 if no other expenses claimed).

Question 6

Do I have to use Making Tax Digital for Income Tax in 2026/27?

Accepted Answer

Yes, if your qualifying income from self-employment and property was over £50,000 in the 2024/25 return — MTD for Income Tax became mandatory for that group from 6 April 2026. You keep digital records and send quarterly updates by 7 August 2026, 7 November 2026, 7 February 2027 and 7 May 2027, then a final declaration by 31 January 2028. The threshold drops to £30,000 from April 2027 and £20,000 from April 2028. Payment dates are unchanged: 31 January and 31 July.

Self Assessment Calculator (UK)

Self-Employed Tax Calculator

Your Self Assessment timeline for 2026/27

What this means for your January bill

Frequently Asked Questions

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Not sure which calculators you need?

Self Assessment Calculator (UK)

Self-Employed Tax Calculator

Your Self Assessment timeline for 2026/27

What this means for your January bill

Frequently Asked Questions

1Who needs to file a UK Self Assessment tax return?

2What are the Self Assessment deadlines for 2026/27?

3What are payments on account?

4What's the penalty for filing Self Assessment late?

5What expenses can I claim on Self Assessment?

6Do I have to use Making Tax Digital for Income Tax in 2026/27?

What's Next?

Sole Trader Tax Calculator

Self-Employed Tax Calculator

Side Hustle Tax Calculator

Not sure which calculators you need?