HMRC CT600 Filing Date

[Mercede5]

Last year We extended the accounting period by 6 months so the new year end was Dec 2025. The accounts for that period have been filed with companies house and I filled in the CT600 for July 2024 - June 2025. I now need to complete the CT600 for the months July 2025 - Dec 2025 but when i look at the HMRC website the date for corporation tax is showing as June 2026. I belive this should have been changed when we extended the accounting period. Do I need to contact HMRC to change this, and will I get into trouble for not changing this before?

We don't owe any corporation tax, and are not trading anymore, but we are still active on companies house whilst we finish paying off the bounce back loan, which will be paid off Next month. After that we will be striking the company off.

Thank you in advance for any advice.

 

[AI Helper]

Companies House and HMRC don't talk to each other on this. Changing your accounting reference date with Companies House (the AA01 form) only updates the Companies House side. HMRC has to be told separately, which is why your business tax account is still showing a July to June pattern and expecting the next period to end June 2026.

The way HMRC handles an 18-month period is exactly as you've done it: one 12-month CT600 (July 2024 to June 2025) and a second short one for the remaining 6 months (July to December 2025). The snag is that HMRC's system will only accept a return for a period it knows about, so if you try to file for July to December 2025 right now it will likely bounce.

What to do:

• Log in to the business tax account, go to the Corporation Tax section and look for the option to tell HMRC about a change to your accounting period. You can update the period end date there.
• If that doesn't work or the option isn't showing, ring the Corporation Tax helpline or write to Corporation Tax Services with the company UTR, explaining the period has been extended and now ends 31 December 2025. They'll amend the record and issue a fresh notice to deliver.

Will you be in trouble? No. There's no penalty just for telling HMRC late about a change of period. Late filing penalties only kick in if a return isn't filed within 12 months of the period end, and your short period only ended in December 2025, so you've got until the end of this year. You're well within time.

One extra point given you're striking off: tell HMRC the company has ceased trading and give them the date. For Corporation Tax purposes an accounting period ends when trading stops, so they may set your final period to run up to that date rather than December. Get the final CT600 filed and confirmed before sending the DS01, as HMRC can object to a strike-off if returns are outstanding. Clearing the bounce back loan first is the right call too, since a lender can also object.