Mistake in my CT600 submission?

[Jezclayton]

Hi and hope you are all well.

I had this nagging doubt in the back of my head and now feel I have made a mistake in the submission. The scenario is as follows.

I am a Director of a close company (Limited) who's year end is 31st December. During the year ended December 2024 a replacement van was purchased for £33,495 and this was included in the CT600 as expenditure qualifying for AIA. This was partially utilised to offset a small trading profit of £15,664, with the balance being carried forward as a loss to be claimed against future profits. This CT600 was filed on 25th September 2025 using the HMRC online software. There was no value recorded in the main pool since the whole value of the van had been claimed as AIA.

So what is the mistake - Upon perusing the figures (the nagging doubt) I realised that no entry (balancing charge?) has been made to account for sale proceeds of my previous van, which amounted to £12,500. If this is correct, my CT600 trading loss to December 2024 is overstated by £12,500 and should be £5,331 as opposed to £17,831.

My CT600 for the year to December 2025 was submitted earlier than usual on 30th March to beat the 31st March deadline for utilising the HMRC software. Unfortunately I did not realise the potential mistake until today, 1st April. The net result is that I have shown a CT600 trading loss for 2025 amounting to £8,958, which should actually be a CT600 trading profit of £3,542.

Assuming both my return for 2024 and 2025 are incorrect and I can no longer put in an amended return using the HMRC software (discontinued) how am I best advised to notify the error. Also, do I need to file amended accounts to Companies House to include the relatively small corporation Tax liability.

 

[Ziggy2024]

You don't need to revise your accounts for this as these are tax adjustments, you will need to file amended returns for 24 / 25 though. How are you planning to file the returns from this year, can you use this solution to file amended returns?

Don't forget that you also need to add back the profit / loss on disposal of the van that should be included in the p&l section of your accounts.

 

[MyAccountantOnline]

If I'm reading it correctly the 2025 accounts will need to be amended as tax is now due.

 

[MyAccountantOnline]

...

Assuming both my return for 2024 and 2025 are incorrect and I can no longer put in an amended return using the HMRC software (discontinued) how am I best advised to notify the error. Also, do I need to file amended accounts to Companies House to include the relatively small corporation Tax liability.

I know TaxCalc sell software you can use if you want to do it yourself. Someone else may be able to offer another alternative. The software accountants such as myself is for multi client/users.

You will need to amend the 2025 accounts for HMRC and Companies House to include the tax due.

 

[Ziggy2024]

If I'm reading it correctly the 2025 accounts will need to be amended as tax is now due.

I wouldn't amend for that, just include in the current year as a under / over provision.

 

[Jezclayton]

You don't need to revise your accounts for this as these are tax adjustments, you will need to file amended returns for 24 / 25 though. How are you planning to file the returns from this year, can you use this solution to file amended returns?

Don't forget that you also need to add back the profit / loss on disposal of the van that should be included in the p&l section of your accounts.

Pretty confident the P@L is correct and does reflect the difference between written down value and proceeds realised upon disposal. Since the funds to purchase the vehicle were provided by myself the Directors loan account entry consisted of the balance payable after any trade-in value.

If it is the situation that any amendment to the CT600 return after 31st March now needs to be done through new software I guess that will be the route I need to take.

Thank you so much for your input.

 

[Jezclayton]

I wouldn't amend for that, just include in the current year as a under / over provision.

I am inclined to adopt this approach since the prospective tax burden of £665 doesn't strike me as particularly significant in the overall scheme of things.