Self Assessment deadlines for the 2026/27 tax year

The 2026/27 tax year runs from 6 April 2026 to 5 April 2027, but the dates that matter for it stretch from January 2027 to July 2028. Here is each one in order, what it means and what happens if you miss it.

Checked for 2026/27 — uses the rates for 6 April 2026 to 5 April 2027, last reviewed 27 October 2026.

The 2026/27 dates at a glance

Date	What is due
31 January 2027	First payment on account for 2026/27 (if you have to make them)
5 April 2027	The 2026/27 tax year ends
31 July 2027	Second payment on account for 2026/27
5 October 2027	Deadline to register for Self Assessment if 2026/27 is your first year
31 October 2027	Paper tax return deadline
30 December 2027	File online by now if you want tax under £3,000 collected through your PAYE code instead
31 January 2028	Online tax return deadline, balancing payment for 2026/27 and first payment on account for 2027/28
31 July 2028	Second payment on account for 2027/28

Registering: 5 October 2027

If you started working for yourself, began letting a property or picked up any other untaxed income during 2026/27, HMRC needs to hear from you by 5 October 2027. Registering as a sole trader gets you a Unique Taxpayer Reference (UTR), which arrives by post and is needed before you can file. It can take a couple of weeks to arrive, so leaving this until the autumn squeezes everything that follows.

You generally do not need to register if your only extra income was trading income of £1,000 or less (covered by the trading allowance) or property income of £1,000 or less. If you are already in Self Assessment from an earlier year, there is nothing to register — just file as usual.

Filing the return: 31 October 2027 or 31 January 2028

Very few people still file on paper, but if you do, the deadline is 31 October 2027. Online returns have three more months, until midnight on 31 January 2028. You can file any time after the tax year ends on 5 April 2027, and filing early has real advantages: you know your bill months before you have to pay it, and any refund (common for CIS workers) arrives sooner.

If you also have a job and your bill is under £3,000, filing online by 30 December 2027 lets HMRC collect it through your tax code over the following year rather than as a lump sum — handy if cash is tight.

Paying: 31 January 2028

Whatever you still owe for 2026/27 — the balancing payment — must reach HMRC by 31 January 2028. Note that the money has to arrive by then, not just leave your account, so bank transfers made on the day itself can be cutting it fine. You can pay by bank transfer, debit card, or in instalments through a budget payment plan set up in your HMRC account during the year.

Payments on account: 31 January and 31 July

Payments on account are advance instalments towards the next year's bill. HMRC asks for them when:

your last Self Assessment bill was more than £1,000, and
less than 80% of your total tax was collected at source (for example through PAYE on a salary).

Each payment is half of the previous year's bill. For 2026/27 they fall on 31 January 2027 and 31 July 2027, based on what you owed for 2025/26. When you file your 2026/27 return, any difference is settled in the balancing payment on 31 January 2028, along with the first payment on account for 2027/28.

This is why the first full year of self-employment can hurt. Say your 2026/27 bill is £4,000 and it is your first year. On 31 January 2028 you pay the £4,000 balance plus £2,000 on account for 2027/28 — £6,000 in a single day — and another £2,000 on 31 July 2028. Our self-employed tax calculator shows this figure for your own numbers.

Can you reduce payments on account?

Yes. If you expect your profit to fall — you worked fewer months, lost a big client or had higher costs — you can ask HMRC to lower your payments on account, either online in your HMRC account or with form SA303. Be realistic: if you reduce them too far and the final bill turns out higher, HMRC charges interest on the shortfall from the original due dates.

Missing a deadline

HMRC's charges fall into three groups. For an ordinary Self Assessment return, a late return triggers an initial £100 penalty, even if you owe nothing or are due a refund, and further penalties build up the longer it stays outstanding. Separately, interest runs on any tax paid late from the day after it was due, and late-payment penalties are added once tax has been outstanding for a set period.

If you are in Making Tax Digital for Income Tax, late-submission penalties work differently: each missed submission earns a penalty point, and a fine only arrives once you reach a set number of points. Late payment is still charged separately.

If something genuinely outside your control stopped you — serious illness, a bereavement, a system failure — you can appeal a penalty, but you need to put things right as soon as you are able.

A simple plan for the year

Every month: move a set amount for tax into a separate savings account. Work the figure out once with a take-home calculator and revisit it when your income changes.
As you go: keep your income and expenses up to date in a spreadsheet or app rather than reconstructing them from bank statements in January.
April to June 2027: once the tax year closes, total your figures while they are fresh.
Summer or autumn 2027: file the return. You still pay on 31 January 2028, but now you know exactly how much.
January 2028: pay the balance and any payment on account from your tax pot.

Treat every date above as a backstop rather than a target, and the January rush becomes a ten-minute payment instead of a weekend of receipts.

Frequently asked questions

When is the Self Assessment deadline for 2026/27?

The online return and the payment of any tax you still owe are both due by 31 January 2028. Paper returns are due earlier, by 31 October 2027.

When do I need to register for Self Assessment?

By 5 October 2027 if 2026/27 is the first tax year you have income that needs reporting, such as profit from self-employment or rental income over £1,000.

Why am I being asked to pay next year's tax in advance?

These are payments on account. They apply when your previous bill was over £1,000 and less than 80% of your tax was collected at source. Each one is half of the previous year's bill, due on 31 January and 31 July.

What happens if I file my return one day late?

For a standard Self Assessment return HMRC charges an automatic £100 penalty, even if there is no tax to pay. More penalties are added if it stays late for longer, and interest runs on any unpaid tax.

Can I file my 2026/27 return early?

Yes — from 6 April 2027 onwards. Filing early does not move the payment date forward; you still have until 31 January 2028 to pay, but you will know the amount in good time.

Estimates only, not tax advice. These figures are a guide based on the information you enter and the 2026/27 rules. Your own position can differ — check GOV.UK or an accountant before relying on them.

A short, plain email before the dates that matter to the self-employed: the 31 January and 31 July payments, the October registration cut-off and Making Tax Digital quarterly updates. No spam.