Amend Dates on submitted CT600 | TinyTax Community
Back to Community
1

Amend Dates on submitted CT600

I cannot amend the dates on my already submitted. I received a letter by HMRC saying my dates overlap. I need to change box 35 from the 29th Feb to 1st March, but the system won't let me. (Even though my old year end was 28th Feb, is this a leap year issue?)

4 Comments

R
Ravi Parmar 9 Feb 2026 at 20:52
I meant box 30 Period start date, not 35.
T
Tim Fouracre Staff 10 Feb 2026 at 19:54
Thanks for getting in touch about this.

We've looked into your filing and can see the CT600 was submitted with a period start of 29 February 2024 — which matches what Companies House reports for your company's accounting period.

To help us understand what HMRC is flagging, could you share the letter they sent you (a photo or scan is fine)? Specifically, we need to see what dates HMRC says are overlapping.

It would also help to know what dates your previous accountant used when they filed your first-year CT600 (the one covering the period ending February 2024). If you have a copy of that return or can check with them, that would narrow things down quickly.

Once we've seen the letter we can get this sorted for you.
R
Ravi Parmar 12 Feb 2026 at 10:23
Hi Tim,
Thanks for the reply, do you have an email or way I can send these documents to you?

I've checked my dashboard on the gov site and although my company house return is 28th Feb, my company tax date ended 29th Feb 2024.
I've called HMRC Corp Tax this morning and they have confirmed, these accounts have been rejected and I need to resubmit with date starting 01/03/24
T
Tim Fouracre Staff 12 Feb 2026 at 11:43
You can email the documents to hello@tinytax.co.uk.

Thanks for checking with HMRC and confirming that. The issue is that your previous accountant's CT600 covered a period ending 29 February 2024, so the next period needs to start on 1 March 2024 to avoid the overlap.

Once we've received the HMRC letter, we'll get the period start date corrected and help you resubmit.