While tax deadlines might not be the most exciting part of business ownership, missing one can lead to penalties, interest charges and unnecessary stress. Staying organised and knowing what’s coming up can make a huge difference. To help, we’ve pulled together a list of the key UK tax deadlines every business owner should have in their diary. But first, why do tax deadlines matter?
HMRC operates on strict timelines. Filing or paying late results in automatic penalties, interest on outstanding amounts, compliance checks and even damage to cash flow. Planning also allows you to manage payments more effectively, spot issues early and avoid last-minute panic.
Self-assessment (sole traders and partners)
If you’re a sole trader or in a partnership, self-assessment is a major annual obligation. The key dates for your diary are -
- 31st January 2026: Online tax return filing deadline and payment of any tax owed for the previous tax year.
- 31st January 2026: First payment on account for the current tax year (if applicable).
- 31st July 2026: Second payment on account due.
If you miss the end of January deadline, penalties start immediately and increase the longer the delay continues.
Corporation tax
If you run a limited company, Corporation Tax deadlines are based on your accounting period. Your key dates are:
- 12 months after your accounting period ends. File your corporation tax return (CT600).
- 9 months and 1 day after your accounting period ends - Pay corporation tax.
For example, if your year-end is the 31st March, your tax payment is due by the 1st January, and the return must be filed by the following 31st March.
VAT returns & payments
If your business is VAT registered, you’ll usually submit returns quarterly underthe MTD (Making Tax Digital).
So, if your quarter ends on the 31st March, your VAT is due by the 9th May. Late VAT submissions are now monitored under HMRC's penalty points system, so consistency really matters here!
PAYE & Payroll
If you employ staff, PAYE deadlines are frequent and important. Some key dates for your diary are -
- 22nd of each month - PAYE and NI payment deadline if paying electronically (19th if by post).
- On or before payday, you must submit your Full Payment Submission (FPS).
- By the 6th July, you must report employee benefits and expenses (P11D forms).
Construction Industry Scheme (CIS)
For construction businesses, CIA adds another layer; your key dates are the CIA return deadline by the 19th of each month, and the 22nd of each month if paying electronically.
Missing CIS deadlines can result in automatic penalties even if no tax is due.
Confirmation Statement & Accounts at Companies House
Although not tax payments, Companies House deadlines are just as important. The crucial dates for your diary are:
- Annually - Confirmation Statement is due.
- 9 months after year-end - First year accounts deadline (or 21 months from incorporation)
- Every year, your accounts are due 9 months after your accounting period ends.
Failing to file can lead to late filing penalties and even strike-off action.
Planning makes life easier!
Rather than reacting to deadlines, successful SME owners build them into their business routine. Keep a central tax calendar, review cash flow ahead of payment dates and set reminders well in advance. Speak to your accountant early if something changes!
Good planning turns from a last-minute scramble into a manageable part of running your business.
We work closely with SME business owners to stay compliant, reduce tax risk and plan with confidence. From VAT and payroll to Corporation Tax and Self Assessment, our expert team makes sure that deadlines are met and opportunities aren’t missed.
If you’d like support in keeping your business tax-efficient and stress-free, get in touch with your Haines Watts team.
