Guide
Corporation Tax annual compliance checklist
Year-end checklist to verify your Corporation Tax compliance is complete.
UK-wide
Check your Corporation Tax compliance every year. Pay your tax 9 months and 1 day after your accounting period ends. File your CT600 form 12 months after it ends. Keep records for 6 years.
- Pay Corporation Tax 9 months and 1 day after accounting period ends
- File CT600 form 12 months after accounting period ends
- Keep records for 6 years
- Keep asset records longer if assets last over 6 years
- For accounting period ending 31 March 2025: pay by 1 January 2026, file by 31 March 2026
- Payment must be made before CT600 filing deadline
- Records must be kept longer if return filed late or HMRC checks
- Late payments or filings may result in penalties and interest
- CT600 form reports profits, losses and tax due
- File accounts at Companies House 9 months after period ends
Annual Corporation Tax checklist
Use this checklist to verify your Corporation Tax compliance at the end of each accounting period. Missing any of these steps can result in penalties, interest, or lost tax relief.
Key deadlines summary
For an accounting period ending 31 March 2025:
- Pay Corporation Tax: 1 January 2026 (9 months + 1 day)
- File accounts at Companies House: 31 December 2025 (9 months)
- File CT600 with HMRC: 31 March 2026 (12 months)
Remember: the payment deadline comes before the filing deadline. Do not wait until you file the CT600 to pay.
Late filing penalties
Penalty:
20% of unpaid tax plus £1,600 in flat penalties
<p>CT600 late filing penalties are automatic:</p>
<ul>
<li><strong>1 day late:</strong> £100</li>
<li><strong>3 months late:</strong> Another £100</li>
<li><strong>6 months late:</strong> HMRC estimates your tax and adds 10% of the unpaid amount</li>
<li><strong>12 months late:</strong> Another 10% of unpaid tax</li>
</ul>
<p>If your CT600 is late 3 times in a row, the £100 penalties increase to £500 each.</p>
<ul>
<li><strong>1 day late:</strong> £100</li>
<li><strong>3 months late:</strong> Another £100</li>
<li><strong>6 months late:</strong> HMRC estimates your tax and adds 10% of the unpaid amount</li>
<li><strong>12 months late:</strong> Another 10% of unpaid tax</li>
</ul>
<p>If your CT600 is late 3 times in a row, the £100 penalties increase to £500 each.</p>