UK tax deadlines — the ones that actually bite
A plain-English calendar for the current tax year: self-assessment, VAT, corporation tax, Companies House and MTD quarters.
Published 24 September 2026 · 5 min read · Figures last checked 23 September 2026 against GOV.UK
Most tax deadlines are dull until one is missed. Then a client is paying a penalty and your practice is writing the apology. This is the calendar I keep for the practices I work with, in plain English, for 2026/27.
The shape of the year
The UK tax year runs from 6 April to 5 April, so 2026/27 runs from 6 April 2026 to 5 April 2027.
Self-assessment for 2025/26
- 5 October 2026 — register for self-assessment. This catches anyone newly self-employed, or with new untaxed income, in 2025/26.
- 31 October 2026 — paper returns.
- 30 December 2026 — online returns, if the client wants the tax collected through their PAYE code rather than paid in one go.
- 31 January 2027 — online returns, the balancing payment for 2025/26 and the first payment on account for 2026/27.
- 31 July 2027 — the second payment on account.
VAT
Returns and payments are due one calendar month and 7 days after the end of the VAT period. Every client has their own stagger, so this is one deadline per client, not one per practice.
The registration threshold is £90,000 of taxable turnover, tested two ways: a rolling 12-month look back, and a forward look at the next 30 days alone.
Corporation tax and Companies House
- Corporation tax is paid 9 months and 1 day after the end of the accounting period.
- The CT600 is filed within 12 months of the period end.
- Companies House accounts are due 9 months after the year end, or 21 months from incorporation for a company's first accounts.
The payment date comes before the filing date. A company with a March year end needs draft numbers by December, not the following March.
MTD for Income Tax
Since 6 April 2026, sole traders and landlords with qualifying income over £50,000 keep digital records and send quarterly updates through MTD-compatible software. The updates are due on 7 August, 7 November, 7 February and 7 May. The April 2027 wave brings the threshold down to £30,000; I have written about who that catches.PAYE benefits
P11D forms are due by 6 July after the tax year ends. It sits outside the year-end rush, which is why it gets missed.
The calendar in one table
| Deadline | Date | Who it bites |
|---|---|---|
| P11D forms for 2025/26 | 6 July 2026 | Employers providing benefits in kind |
| MTD quarterly updates | 7 August, 7 November, 7 February, 7 May | Mandated sole traders and landlords |
| Register for self-assessment | 5 October 2026 | Newly self-employed; new untaxed income |
| Paper self-assessment return | 31 October 2026 | Clients who still file on paper |
| Online return for PAYE coding-out | 30 December 2026 | Employed clients with a small tax bill |
| Online return, balancing payment, first payment on account | 31 January 2027 | Every self-assessment client |
| Second payment on account | 31 July 2027 | Clients with payments on account |
| VAT return and payment | Period end plus 1 month and 7 days | Each VAT-registered client, on their own stagger |
| Corporation tax payment | 9 months and 1 day after period end | Every company with tax to pay |
| CT600 | 12 months after period end | Every company |
| Companies House accounts | 9 months after year end (21 months for first accounts) | Every company |
One date that can change the others
The Autumn Budget 2026 is scheduled for 28 October 2026. Thresholds and rates on this site are re-checked against GOV.UK after each Budget, and each post’s “last checked” date is updated when that happens.What I do about it for practices
- Deadline tracking per entity. Every client I touch has its own line: VAT stagger, accounting period, CT payment date, filing date, self-assessment status.
- Cover notes with every file. Each job comes back with a short note listing the judgements I made, the open points, and the next date that matters for that client.
- Early questions. If a set of records will not support a deadline, you hear at the start of the week, not the day before.
If that rhythm would help your practice, here is how I work with UK practices.