UK Self-Employed Tax Deadlines: The Complete 2026/27 Calendar

Missing a tax deadline costs money — usually £100 immediately, then £10 per day, then a percentage of the unpaid tax. None of these penalties are negotiable unless you have a reasonable excuse, and HMRC's definition of "reasonable" is narrower than most people expect. The single most effective thing a self-employed person can do to reduce their tax stress is to know every deadline in advance and build them into their calendar at the start of each tax year.

This is the full calendar for 2026/27.

The tax year itself

The UK tax year runs from 6 April to 5 April the following year. The 2026/27 tax year runs from 6 April 2026 to 5 April 2027. Your Self Assessment return for 2026/27 will be due in the following tax year — 2027/28 — with a filing deadline of January 2028. This one-year lag is where most new self-employed people get confused.

When people talk about the "January deadline" each year, they mean filing the return for the previous tax year. So in January 2027, you'll be filing for 2025/26 income. In January 2028, you'll file for 2026/27.

The key annual deadlines

5 October — Register for Self Assessment

If you became self-employed during the 2026/27 tax year and have not previously been in Self Assessment, you must register with HMRC by 5 October 2027 (the October following the end of the tax year). Missing this doesn't automatically trigger a penalty, but it means HMRC won't send you a notice to file, and you'll still be liable for any tax owed — along with interest if payment is late.

Register through your Government Gateway account at gov.uk/register-for-self-assessment. If you already have a Unique Taxpayer Reference (UTR) from a previous Self Assessment period, you don't need to re-register — just submit your return as normal.

31 October — Paper return deadline

If you want to file your Self Assessment tax return on paper rather than online, the deadline is 31 October following the end of the tax year. For 2025/26 income, that's 31 October 2026. Paper filing is available but increasingly uncommon — HMRC encourages online filing, and the January deadline gives you three extra months if you file digitally.

31 January — Online return and tax payment

The most important deadline of the year: 31 January. This is the deadline for:

Filing your Self Assessment tax return online for the previous tax year
Paying any tax owed for that year (the "balancing payment")
Making your first payment on account for the current tax year (if applicable)

For the 2025/26 tax year, that means 31 January 2027. Miss this date and the £100 immediate penalty clock starts instantly — even if you owe no tax.

The 31 January deadline is fixed. Banks breaking down, post being slow, accountants being unavailable — none of these are acceptable excuses to HMRC. File and pay early enough that technical problems can be resolved before the deadline.

31 July — Second payment on account

If you make payments on account (advance tax payments), the second instalment is due on 31 July. For the 2026/27 tax year, that means 31 July 2027. This is half of the previous year's tax bill, paid in advance toward the current year's liability. Use the Payment on Account Calculator to understand what you're likely to owe and when.

VAT deadlines (if VAT-registered)

If your business turnover exceeds the VAT registration threshold (£90,000 as of April 2024), you must register for VAT and file regular VAT returns. Under Making Tax Digital for VAT, all VAT-registered businesses must file using compatible software.

VAT returns are typically quarterly. The due date is one calendar month and seven days after the end of the VAT period. So if your quarter ends 31 March, your return and payment are due 7 May.

Your specific quarter dates depend on when you registered for VAT. HMRC confirms your stagger group when you register.

Annual VAT accounting is available to businesses with turnover below £1.35 million — under this scheme you make monthly or quarterly advance payments and file a single annual return.

PAYE and CIS deadlines (if applicable)

If you employ staff, PAYE submissions are due on or before each pay date. The PAYE liability for each month is due to HMRC by the 19th of the following month (22nd if paying electronically).

Under CIS, contractors must file monthly CIS returns by the 19th of each month covering deductions made in the previous tax month. Sub-contractors can reclaim CIS deductions through their Self Assessment return or, if employed, through their employer.

National Insurance contributions

Class 4 NI is calculated and collected through Self Assessment — it appears on your SA return alongside your income tax liability, and is due by the same 31 January and 31 July deadlines as income tax payments on account.

Class 2 NI (effectively abolished for those with profits above the Small Profits Threshold from 6 April 2024) no longer requires separate payment for most people. Where voluntary Class 2 is paid, it appears on the SA return.

What happens if you miss the 31 January deadline

HMRC applies automatic penalties for late filing and late payment:

Late filing penalties:

Day 1 (1 February): £100 fixed penalty — applies even if you owe nothing
After 3 months: £10 per day, up to a maximum of £900
After 6 months: 5% of tax owed (or £300 if greater)
After 12 months: a further 5% of tax owed (or £300 if greater) — or higher rates if HMRC believes the failure was deliberate

Late payment penalties:

30 days late: 5% surcharge on unpaid tax
6 months late: additional 5% surcharge
12 months late: additional 5% surcharge
Interest accrues from the due date until payment, currently at Bank of England base rate + 2.5%

Reasonable excuse appeals

You can appeal a penalty if you have a "reasonable excuse" — a genuine, unforeseeable event that prevented you from filing or paying on time. Serious illness, bereavement of an immediate family member close to the deadline, or a Government Gateway technical failure on the deadline itself may qualify. Forgetting, not knowing about the deadline, or having an accountant fail to file do not typically qualify.

Appeals must be made within 30 days of receiving the penalty notice, in writing to HMRC.

Planning around the deadlines

The most useful habit is to set calendar reminders for four dates at the start of each tax year:

31 July — second payment on account due
5 October — registration deadline for new SA taxpayers
31 January — return filing and full payment due
Month-end after each VAT quarter — VAT return due (if applicable)

Use the Self Assessment Estimator throughout the year to build up an estimate of your bill so that 31 January is never a surprise. Setting aside 25–30% of each payment you receive into a separate savings account is the simplest way to ensure the money is there when HMRC asks for it.