Running a small business in the UK requires more than just great products or services — staying on top of your tax obligations is equally crucial. Missing a deadline can lead to penalties, cash flow issues, and unnecessary stress. To help you stay compliant and organised, we’ve outlined the key UK tax deadlines for 2025 that every small business owner must know.
Key Tax Deadlines for Small Businesses in 2025
Below is a month-by-month breakdown of the most important tax dates that apply to sole traders, limited companies, and employers.
✅ January 2025
- 31 January 2025
- Self-Assessment Tax Return Deadline (for tax year 2023/24)
- Balancing payment for 2023/24 tax year due
- First payment on account for 2024/25 also due (if applicable)
- Late filing penalty of £100 applies from 1 February
✅ April 2025
- 5 April 2025
- End of the 2024/25 tax year
- 6 April 2025
- Start of the 2025/26 tax year
- Employers should prepare to issue:
- P60s by 31 May 2025
- P11Ds by 6 July 2025
✅ July 2025
- 6 July 2025
- Deadline to file P11D and P11D(b) forms for benefits and expenses
- 31 July 2025
- Second Payment on Account for 2024/25 (for self-employed and sole traders)
✅ October 2025
- 5 October 2025
- Deadline to register for Self-Assessment if you became self-employed during 2024/25
- 31 October 2025
- Paper Self-Assessment tax return deadline (only if not filing online)
✅ December 2025
- 30 December 2025
- If you want HMRC to collect tax through your tax code (PAYE), you must file online by this date (and owe less than £3,000)
💼 Other Important Deadlines
Corporation Tax
- 9 months and 1 day after the end of your company’s financial year – payment is due
- 12 months after your year-end – deadline to file Company Tax Return (CT600)
VAT
- Monthly or quarterly depending on your VAT scheme – usually due 1 month and 7 days after the period ends
PAYE & CIS
- Monthly payments due by the 22nd of each month (or 19th if paying by post)
⚠️ Penalties for Missing Deadlines
HMRC charges penalties for:
- Late submission of tax returns
- Late payments
- Inaccurate filings
These can start from £100 and increase depending on how late or inaccurate your submission is. Interest is also charged on unpaid tax.
💡 Tips to Stay Compliant
- Set calendar reminders for all deadlines
- Use accounting software to automate calculations and filing
- Hire a qualified accountant or advisor
- File returns early — don’t wait until the last minute
✅ How MZMC Can Help
At MZMC Accounting & Digital Services, we offer tax planning, compliance, and filing services tailored for small businesses in Scotland and across the UK. We’ll help you:
- File returns accurately and on time
- Avoid penalties and interest
- Plan your cash flow around tax obligations
📩 Book a Consultation to discuss how we can support your business in 2025.