UK accounting filing deadlines in 2026: the complete calendar

For a UK practice, the calendar is the job. Miss a Confirmation Statement and Companies House starts a strike-off clock; miss a VAT payment and HMRC's penalty points tick up. This guide sets out the statutory filing deadlines that shape a 2026 workload, and — more usefully — the rule that produces each one, so you can reproduce the date for any client regardless of their year-end.

The fixed dates every UK practice already knows

A handful of deadlines land on the same date for almost everyone, which makes them the anchors of the compliance year:

• 31 January 2026 — online Self Assessment filing and balancing payment for the 2024/25 tax year, plus the first payment on account.
• 6 July 2026 — P11D and P11D(b) returns for expenses and benefits in the 2025/26 tax year.
• 31 July 2026 — second Self Assessment payment on account for 2024/25.
• 7 August 2026 — the first MTD for Income Tax quarterly update, for the quarter to 5 July 2026.
• 5 October 2026 — deadline to register for Self Assessment if you became liable during 2025/26.
• 31 October 2026 — paper Self Assessment filing for 2025/26.

The moving deadlines: worked out per client

Most of a practice's deadlines are not fixed dates at all — they are derived from each client's own year-end or VAT stagger. These are the ones spreadsheets get wrong, because every client has a different anchor.

Annual accounts (Companies House)

Private companies must file accounts within nine months of the accounting reference date (ARD). A company with a 31 March 2026 year-end therefore files by 31 December 2026. A first set of accounts runs 21 months from incorporation instead.

Corporation Tax (HMRC)

Payment is due nine months and one day after the end of the accounting period; the CT600 return is due twelve months after period end. So the same 31 March 2026 year-end means Corporation Tax paid by 1 January 2027 and the return filed by 31 March 2027 — the pay-before-you-file gap that catches out new company directors. Filing that return late now costs £200 on day one: HMRC doubled the fixed penalties for returns due on or after 1 April 2026.

Confirmation Statement (Companies House)

Due within 14 days of the end of the review period. Counted from incorporation, the review period ends the day before the anniversary; after a statement is filed, it ends a year after the date that statement was made up to. It is cheap to file and expensive to forget: Companies House can now issue a financial penalty for a late statement, and a persistently overdue one can trigger strike-off proceedings.

VAT returns and payments (HMRC)

For standard quarterly VAT, the return and payment are both due one calendar month and seven days after the period end. A client on the stagger group ending 31 March 2026 files and pays by 7 May 2026. Since Making Tax Digital, these must be submitted through compatible software.

MTD for Income Tax quarterly updates (HMRC)

Since 6 April 2026, sole traders and landlords with qualifying income over £50,000 send HMRC a quarterly update from compatible software. The updates for the quarters to 5 July and 5 October 2026 are due on 7 August and 7 November 2026; the next two fall on 7 February and 7 May 2027, and the final declaration for 2026/27 is due by 31 January 2028.

The pattern to remember: fixed dates are the same for every client; derived dates change with each client's ARD or VAT stagger. It's the derived dates that need a system, not a spreadsheet.

Weekends and bank holidays

A deadline that falls on a weekend or a UK bank holiday is not pushed to the next working day. GOV.UK is explicit for VAT: the return and the payment must reach HMRC on or before the deadline, even if it is on a weekend or bank holiday. Money also has to clear in time, so in practice a Saturday deadline is a Friday deadline for the payment. Track the statutory date, and plan to finish before it.

Turning the calendar into a system

The safest way to run this is to record each client's anchors once — entity type, ARD, VAT stagger, payroll, Self Assessment and MTD obligations — and let those anchors generate a rolling schedule. That is exactly what FilingKeeper does: you add a client, and every derived deadline appears on its statutory date, with reminders before each one.

This article is general guidance, not tax advice. Always confirm a client's specific obligations against current HMRC and Companies House guidance.