Tax8 April 20265 min read

UK Small Business Tax Dates 2026: Every Deadline You Need to Know

Every tax deadline for UK sole traders and limited companies in 2026. Corporation tax, self assessment, VAT, PAYE, and more.

Why missing a deadline costs you money

HMRC charges automatic penalties and interest the moment you miss a filing or payment deadline. A single day late on self assessment costs you £100. Miss it by three months and it rises to £10 per day on top. Corporation tax paid late incurs interest from day one. These are avoidable costs that no small business should be paying.

Here are every key date for the 2026/27 tax year that UK sole traders and limited companies need in their calendar.

Self assessment (sole traders and partnerships)

5 April 2026 marks the end of the 2025/26 tax year. If you are a sole trader or partner, your self assessment return for 2025/26 is due by 31 January 2027 if filing online. The paper deadline is 31 October 2026. Your payment on account for 2026/27 is also due by 31 January 2027 and 31 July 2027.

If your tax bill for 2025/26 exceeds £1,000, HMRC will require payments on account for the following year. These are two advance payments, each equal to half of the previous year's tax bill. They catch many sole traders off guard because the cash leaves your account before you have earned the full year's income.

Corporation tax (limited companies)

Corporation tax for accounting periods ending in the 2025/26 financial year is due 9 months and one day after your accounting period ends. For a standard March year end, that means 1 January 2027. Your corporation tax return (CT600) must be filed within 12 months of the end of the accounting period.

VAT deadlines

If you are VAT registered, your VAT return and payment are due one month and seven days after the end of each VAT quarter. Standard VAT quarters end on 31 March, 30 June, 30 September, and 31 December. So a return for the quarter ending 31 March 2026 is due by 7 May 2026.

Making Tax Digital means all VAT returns must be filed digitally through compatible software. Xero, QuickBooks, and Sage all support MTD VAT filing.

PAYE and National Insurance

If you employ staff, PAYE and NI contributions are due to HMRC by the 22nd of each month (or 19th if paying by post). RTI submissions (Full Payment Submissions) must be sent on or before each pay date.

How CFO Pal helps

CFO Pal does not file your tax returns. That is your accountant's job. What it does is ensure you have the cash set aside to pay when the deadline arrives. The cashflow forecast models upcoming tax payments so you can see exactly when the money needs to leave your account and plan accordingly.