E · Workflow, deadlines & operations
UK Accountants' Deadline Calendar 2026/27
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Quick answer
The key annual deadlines for UK accountants are 31 January (self assessment online), 31 July (second payment on account), 9 months after year end (private company accounts), 9 months and 1 day after year end (CT payment), 12 months after year end (CT600), and 6 July (P11D). VAT and PAYE run monthly or quarterly, and MTD for Income Tax adds quarterly update deadlines from April 2026.
Key takeaways
- Build one master calendar covering SA, accounts, CT, VAT, PAYE and, from April 2026, MTD ITSA quarterly updates.
- CT payment (9 months + 1 day) falls before the CT600 filing deadline (12 months) — don't confuse the two.
- Companies House confirmation statement (CS01) is due at least once every 12 months, separate from the accounts deadline.
- P11D and P11D(b) are due 6 July following the tax year, with Class 1A NIC paid by 22 July (electronic).
- MTD for Income Tax brings quarterly submission deadlines (roughly one month after each quarter end) for clients over the £50,000 threshold.
- Missed deadlines trigger automatic penalties from HMRC and Companies House — reminders should be set well in advance, not on the day.
What are the self assessment deadlines?
Paper returns are due 31 October, online returns and balancing payment by 31 January, with a second payment on account due 31 July.
Self assessment remains the deadline most clients ask about, and the one most likely to cause a January scramble if records weren't chased earlier in the year. The tax year runs to 5 April, paper returns are due by 31 October following the year end, and online returns, along with any balancing payment, are due by 31 January. A second payment on account, where applicable, falls on 31 July.
Registration for self assessment for a new source of income has its own deadline of 5 October following the tax year in which the income arose. That's easy to miss for new sole traders and landlords who don't think about tax until much later.
What are the company accounts and corporation tax deadlines?
Private company accounts are due at Companies House 9 months after the year end; corporation tax is payable 9 months and 1 day after the year end, with the CT600 filed within 12 months.
These three dates are easy to muddle because they all relate to the same accounting period but fall at different points. Get the sequence wrong in a client conversation and you'll spend the next call clarifying it.
- Corporation tax payment: 9 months and 1 day after the end of the accounting period (for most small companies not paying quarterly instalments).
- Private limited company accounts filed at Companies House: 9 months after the accounting reference date.
- CT600 corporation tax return filed with HMRC: 12 months after the end of the accounting period.
A first set of accounts covering more than 12 months has adjusted filing deadlines, so treat new incorporations as a special case rather than applying the standard rule mechanically.
When is the confirmation statement (CS01) due?
A confirmation statement is due at least once every 12 months, within 14 days of the review period ending, and is separate from the accounts filing deadline.
Because the confirmation statement review period is tied to incorporation date or the last statement date rather than the accounting year end, it frequently falls on a different date to the accounts deadline. It's worth tracking as its own line in the calendar rather than assuming it lines up with year-end work.
What are the VAT and PAYE/RTI deadlines?
VAT returns and payment are normally due one month and 7 days after the end of the VAT period; PAYE/RTI submissions are due on or before each payday, with payment by the 22nd of the following month (electronic).
Most clients are on quarterly VAT stagger groups, so the deadline rotates depending on the group they're assigned. PAYE is more predictable: a Full Payment Submission is due on or before payday, and any tax and National Insurance owed is due by the 22nd of the following month if paying electronically (19th by post).
| Obligation | Deadline |
|---|---|
| Self assessment online + balancing payment | 31 January |
| Second payment on account | 31 July |
| Private company accounts (Companies House) | 9 months after year end |
| Corporation tax payment | 9 months + 1 day after year end |
| CT600 corporation tax return | 12 months after year end |
| Confirmation statement (CS01) | At least every 12 months |
| P11D and P11D(b) | 6 July following the tax year |
| Class 1A NIC payment | 22 July (electronic) |
When are P11D forms due?
P11D and P11D(b) forms reporting benefits in kind are due by 6 July following the end of the tax year, with Class 1A National Insurance paid by 22 July.
Benefits in kind reporting is a frequently underestimated workload spike in early July, particularly for clients with company cars, private medical insurance or loans to directors. Payrolling benefits in real time removes the need for P11D reporting on those specific benefits, which is worth discussing with clients who find July disruptive.
What deadlines does Making Tax Digital for Income Tax add?
From April 2026, qualifying sole traders and landlords with income over £50,000 must submit quarterly updates roughly one month after each quarter ends, plus a final declaration.
MTD for Income Tax adds four quarterly update deadlines per client per year on top of the existing annual self assessment cycle, plus a final declaration replacing the old tax return for that income. For a practice with dozens of affected clients, that's a material increase in the number of deadline events across the year, which is exactly the kind of volume that makes a spreadsheet calendar unmanageable.
How should a practice build its own deadline calendar?
Combine statutory deadlines with internal working deadlines set several weeks earlier, and automate reminders rather than relying on memory or a wall planner.
The statutory deadline is the point of failure, not the target. A well-run practice sets its own internal deadlines — for example, chasing records eight weeks before the CT600 is due, not one week before — and tracks both dates against each client and each job.
How Remindoo helps
Chasing every deadline manually across self assessment, accounts, CT600, VAT, PAYE and now MTD ITSA quarterly updates isn't realistic once a practice has more than a handful of clients. Remindoo generates automated reminders and trigger dates from Companies House, HMRC-related milestones and internal deadlines you set, so each client's obligations surface on a schedule rather than depending on someone remembering. Pair that with recurring tasks and service templates so each deadline type — SA, accounts, CT600, VAT, P11D, MTD quarterly updates — has a standard job with its own internal working deadline built in. As MTD ITSA adds four extra deadline events per client per year, that structure matters more, not less. The result is a practice where deadlines are tracked against the client record and the job, not against someone's memory or a separate spreadsheet that falls out of date.
Frequently asked questions
What is the deadline for filing a CT600?
The CT600 corporation tax return must be filed within 12 months of the end of the accounting period it covers, though the tax itself is due earlier, 9 months and 1 day after the year end.
Is the confirmation statement the same as the annual accounts?
No. The confirmation statement (CS01) confirms company details at Companies House and is due at least every 12 months; annual accounts are a separate filing due 9 months after the year end.
When is the second payment on account due?
The second payment on account for self assessment is due by 31 July, six months after the first payment on account which is due alongside the balancing payment on 31 January.
When do P11D deadlines fall?
P11D and P11D(b) forms are due by 6 July following the tax year, with Class 1A National Insurance contributions due by 22 July if paying electronically.
How often are VAT returns due?
Most businesses file VAT returns quarterly, with the return and payment due one month and 7 days after the end of the VAT period, though staggers vary by registration.
What new deadlines does MTD for Income Tax introduce?
From April 2026, affected sole traders and landlords face quarterly update deadlines roughly one month after each quarter ends, in addition to an annual final declaration.
Do all companies have the same accounting reference date?
No. The accounting reference date is usually the anniversary of the last day of the month of incorporation unless changed, so filing deadlines vary between companies.
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Sources
- GOV.UK — Self Assessment tax returns (opens in new tab)
- GOV.UK — Company Tax Returns (opens in new tab)
- GOV.UK — Annual accounts and confirmation statement (opens in new tab)
- GOV.UK — Expenses and benefits: reporting and paying (opens in new tab)
- GOV.UK — Making Tax Digital for Income Tax (opens in new tab)
Last updated 23 September 2026. General guidance, not legal or regulatory advice. Check with your professional body.
