Self Assessment deadlines and key tax dates for 2026 to 2027

Tax deadlines are not hard to meet. They are hard to remember. Most late filing penalties are not caused by people refusing to pay but by people forgetting that a date was coming. This calendar pulls the key dates for 2026 to 2027 into one place, explains what each one means, and shows what happens if you miss it. Keep it, put the dates in your diary and set a reminder a fortnight ahead of each.

Dates and penalties can be updated by HMRC, so always check the current position on GOV.UK. Everything below reflects the rules at the time of writing.

The tax year and which deadlines apply

The UK tax year runs from 6 April to 5 April. The 2025/26 tax year ended on 5 April 2026. The Self Assessment return for that year is due on 31 January 2027. The 2026/27 tax year runs from 6 April 2026 to 5 April 2027, and is the first year of Making Tax Digital for Income Tax for those with qualifying income over £50,000.

Self Assessment key dates for the 2025/26 return

Date	What it is
5 October 2026	Deadline to register for Self Assessment if you needed to send a return for 2025/26 and had not before
31 October 2026	Deadline for paper returns, now passed
30 December 2026	Deadline to file online if you want HMRC to collect tax up to £3,000 through your tax code
31 January 2027	Online return deadline and payment of any tax due, plus the first payment on account for 2026/27
31 July 2027	Second payment on account for 2026/27

The 31 January date is the one that matters most, because it is both the filing deadline and the payment deadline for the balance.

Payments on account explained

If your Self Assessment bill is more than £1,000, and less than 80% of your tax was collected at source, HMRC asks you to pay in advance. These payments on account are two instalments, each half of your previous year's bill, due on 31 January and 31 July. When you file your return, any difference between what you paid on account and what you actually owe is settled on the following 31 January.

For example, if your 2025/26 bill is £6,000, you will pay £3,000 on 31 January 2027 for the 2026/27 year on account, as well as the £6,000 balance for 2025/26 unless you have already made payments towards it. That can mean a very large payment in January, up to 150% of one year's bill if payments on account have not been previously made. Set money aside every month. Our sole trader tax calculator estimates your bill, and you can reduce payments on account if you expect your income to fall.

Making Tax Digital quarterly updates

If you are in scope for Making Tax Digital for Income Tax, you send a quarterly update for each source of income. For standard quarters, the deadlines are:

• 7 August
• 7 November
• 7 February
• 7 May

Of these, the August and November 2026 deadlines have passed and the next is 7 February 2027, covering 6 October 2026 to 5 January 2027. The final declaration for 2026/27 is due by 31 January 2028. See our Making Tax Digital guide and the post on how quarterly updates work. You can check whether you are in scope with the Making Tax Digital checker.

Penalties for late Self Assessment returns

HMRC applies penalties that escalate with delay.

How late	Penalty
Missed the 31 January deadline	£100, even if you owe no tax
3 months late	Daily penalties of £10 for up to 90 days, a further maximum of £900
6 months late	The greater of £300 or 5% of the tax due
12 months late	A further penalty of the greater of £300 or 5% of the tax due

Late payment attracts interest from the due date and separate penalties at 30 days, 6 months and 12 months, normally 5% of the unpaid tax each time. If you have a reasonable excuse, such as serious illness, you can appeal. Penalties are avoidable by filing early, even if you cannot pay in full, and contacting HMRC about a payment plan.

Other dates worth diarising

VAT. Returns and payments are normally due one month and seven days after each VAT period ends. See our VAT guide.

PAYE. Electronic payments are due by the 22nd of the month after the pay period. Employers also file an Employer Payment Summary and Full Payment Submission on or before payday. See payroll bookkeeping.

CIS. Contractors file the monthly return by the 19th. See CIS bookkeeping.

Companies House and Corporation Tax. Accounts are due 9 months after the company's year-end, Corporation Tax is payable 9 months and 1 day after and the return is due 12 months after. See our limited company bookkeeping guide.

P60 and P11D. Employers give P60s to employees by 31 May and file P11Ds by 6 July.

A practical way to never miss a date

1. Put every date in a calendar with two reminders, one a month ahead and one a week ahead.
2. Reconcile monthly so you are never gathering a year of records at the last minute. Use the monthly bookkeeping checklist.
3. Estimate your tax every quarter and move the money to a separate account.
4. File early. There is no prize for filing on 31 January, but there is no penalty for filing in May either.
5. Ask for help. A bookkeeper can prepare the figures and an accountant can file.

What to do if you have missed a deadline

Do not ignore it. File as soon as you can, because penalties escalate with time. If you cannot pay, still file, then contact HMRC about a payment plan. If your records are behind, our catch-up bookkeeping service rebuilds them quickly, and our guide to catching up on bookkeeping explains the process.

A worked payments-on-account example

Suppose a sole trader's 2025/26 tax bill is £8,000, and she paid nothing on account for that year. On 31 January 2027 she must pay the £8,000 balance and also the first payment on account for 2026/27, which is £4,000, so £12,000 in one go. On 31 July 2027 she pays a second £4,000. When she files her 2026/27 return, any difference between the £8,000 paid on account and her actual bill is settled the following January. This pattern surprises many first-time filers. The solution is to put aside roughly a quarter to a third of profit every month, in a savings account, so the January payment is never a shock.

Frequently asked questions

When is the 2025/26 Self Assessment deadline?

31 January 2027 for the online return and for payment of any tax due.

What happens if I miss the 31 January deadline?

An automatic £100 penalty, with further penalties and interest if the delay continues.

Do I need to file if I earn under the personal allowance?

Not always, but you must file if you are self-employed with income over the trading allowance or have other reportable income. Check HMRC's guidance.

Can I pay my tax bill in instalments?

HMRC offers Time to Pay arrangements in many cases. Contact them before the deadline, not after.

Can you help me prepare for the deadline?

Yes. We keep your records current so your accountant or you can file easily. Get an instant quote.