Running a business is demanding enough without the added stress of missed tax deadlines.
Failing to submit returns or pay tax on time can result in penalties, interest, and unnecessary HMRC attention. Whether you’re a sole trader, limited company director or employer, understanding key UK tax deadlines is essential for staying compliant and protecting cash flow.
In this guide, we break down the most important small business tax deadlines every UK owner should know.
📅 What Are the Key Self Assessment Deadlines?
If you’re a sole trader, partnership member, or company director receiving dividends, you may need to file a Self Assessment tax return.
Here are the key dates:
- 5 October – Register for Self Assessment (if newly self-employed)
- 31 October – Paper tax return deadline
- 31 January – Online tax return deadline
- 31 January – Payment of tax due + first payment on account
- 31 July – Second payment on account (if applicable)
Missing the 31 January deadline triggers an automatic £100 penalty — even if no tax is owed.
👉 If you’re unsure whether you need to file, speak to our team about Self Assessment services.
🏢 When Is Corporation Tax Due for Limited Companies?
If you run a limited company, Corporation Tax deadlines are different from personal tax deadlines.
When must Corporation Tax be paid?
- 9 months and 1 day after your accounting period ends
For example:
If your year end is 31 March 2025, your Corporation Tax payment is due by 1 January 2026.
When must the Company Tax Return (CT600) be filed?
- 12 months after your accounting period ends
Late filing results in automatic penalties starting at £100.
For help managing deadlines and year-end accounts, see our Limited Company Accounting Services.
💼 What Are the VAT Deadlines?
If your business is VAT registered (threshold currently £90,000 turnover — always check current HMRC rules), you must submit VAT returns regularly.
Most businesses file quarterly VAT returns.
When are VAT returns and payments due?
- Usually 1 month and 7 days after the end of your VAT quarter
For example:
VAT quarter ending 31 March → deadline is 7 May.
Under Making Tax Digital (MTD), VAT returns must be filed digitally using compatible software.
Read more about this in our blog on Making Tax Digital Explained.
👥 What Are PAYE and Payroll Deadlines?
If you employ staff, you must operate PAYE.
What are the monthly PAYE deadlines?
- 22nd of each month (if paying electronically)
- 19th of each month (if paying by post)
You must also:
- Submit RTI (Real Time Information) reports on or before each payday
- File P60s by 31 May
- Report expenses/benefits (P11D) by 6 July
Late PAYE payments trigger penalties that increase with repeated delays.
If payroll is taking up too much of your time, consider outsourcing through our Payroll Services.
🗂 What Are the Companies House Deadlines?
Limited companies must also file with Companies House.
When are annual accounts due?
- 9 months after your financial year end
When is the Confirmation Statement due?
- 12 months after incorporation or last filing
Late filing penalties start at £150 and increase rapidly.
❓ What Happens If You Miss a Tax Deadline?
HMRC penalties can include:
- Fixed fines
- Daily penalties
- Interest on overdue tax
- Increased scrutiny or investigation risk
Repeated late filings can damage your business credibility — especially when seeking finance or investment.
🧾 How Can You Keep Track of All These Deadlines?
Many small business owners struggle because:
- Personal and company tax deadlines differ
- VAT quarters vary
- Payment on account rules are confusing
Working with an accountant ensures:
✔ Deadlines are monitored
✔ Reminders are sent
✔ Returns are filed correctly
✔ Tax liabilities are planned in advance
If you’d like support managing your compliance, contact Atreus Accountants today.