Hi there,
Thanks for the clear question. You're right: the earlier return needs to be amended so the loss reduces its taxable profit.
Where to enter it
Open the earlier filing and start an amendment.
Go to the Profit & Loss step, then Tax Adjustments.
Find the field "Trading losses carried back from a later period (£)".
Does WeFile pick it up automatically?
Partly:
If the later return was filed with WeFile, a note appears under the field. It shows the later filing's reference, its period and the amount it carries back. Click Apply to fill in that amount. We don't fill it in without your confirmation, so it's always your choice.
If the later return was filed somewhere else, type the carried-back amount into the field yourself.
What happens on the CT600
The amount goes into box 275, rounded down to whole pounds, and box 280 is ticked to show the relief comes from a later period.
The relief can't be more than the profits available that year. It's applied before qualifying donations.
The Corporation Tax is recalculated automatically, and you can check the updated CT600 and tax computation before you submit.
Submitting the amendment
On the Credentials step, choose "CT600 only". A loss carry-back doesn't change your statutory accounts, so nothing needs to be filed again with Companies House. Once HMRC processes the amendment, it will repay the overpaid tax or set it against anything the company owes.