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How do I carry back a loss to a previous financial year on a CT600?

Article ID: 828
Last updated: 29 Apr, 2021

Carrying back trading losses

A company incurring a trading loss in an accounting period can make a claim to offset the loss against total profits of the previous 12 months after first having set the losses against any profits of the accounting period in which the loss occurred.

The Budget 2021 and Finance Bill has introduced a new extended loss carry back for businesses subject to income and corporation tax, giving the opportunity to make the most of any trading losses related to the pandemic.

Trade loss carry back is extended from the current 1 year entitlement to a period of 3 years, with losses being carried back against later years first. This extension will apply to trading losses made by companies in accounting periods ending between 1 April 2020 and 31 March 2022. 

How to claim loss relief on a CT600

HMRC claims that as long as box 45 for 'Claim or relief affecting an earlier period' is ticked on the current year return, you should not need to re-file the amendment for the earlier year.  This being said, customers have previously reported that although this box is ticked, the repayment has not been issued and therefore an amendment of the earlier year was required to issue this repayment. How you make the claim will depend on how far back you wish to carry back the loss. For more information on timescales of filing amendments, please see the article for What tax years can I file online?

Entries to make for the current return period in which the losses have arisen (V3 form 2020)

HMRC Forms Mode: 

  1. Within the CT600 > Go to CT600 Core > Page 1 > Tick Box 45

2. Go to CT600 Core > Computations > Losses, Management Expenses, NTLRDs and NTLIFA’s >Trading Losses > Insert the loss in the box for ‘‘Carried back against profits of a previous period’’

3. Switch to SimpleStep mode

4. Go to Finalising the return

5. Tick the box for an earlier period?

Please note:

Once these entries are completed, you may then process the current period submission as usual. If the period being amended for the losses being carried back, falls outside of the amended return filing window, you may still amend the return to send to HMRC as a paper return, alternatively, you can write to them with the details of the loss, (explained at the end of this article).

If you would like to process an amendment for the earlier year, please complete the entries as described below. Instructions are given for both version 3 and version 2 of the CT600 forms, depending upon how far back your return period is.  

Entries to make for the previous year return period(s) in which loss relief is being claimed: Return period starting on or after 01/04/15

HMRC Forms mode (Version 3)

  1. Go to CT600 Core > Core > Page 1 > Tick Box 40 'A repayment is due for this return period'
  2. Go to CT600 Core > Core > Page 6 > Insert the corporation tax previously paid, into Box 595 'Tax already paid (and not already repaid)'
  3. Go to CT600 Core > Computations > Losses, Management Expenses, NTLRDs and NTLIFAs > Trading Losses > Insert the loss in the box for ‘’Trading losses of a later accounting period utilised’’
  4. Complete the additional boxes on CT600 Core > Page 10 and as appropriate
  5. If you want to add any notes which would usually be covered in an additional information box, please click on: Computation Management > Edit Notes > Select the location where you want to place the information save this as required

Simple Step mode (Version 3)

  1. Go to CT600 Core > Losses, Management Expenses, NTLRDs and NTLIFAs > Trading Losses > Insert the loss in the box for ‘’Trading losses of a later accounting period utilised’’
  2. Go to Tax reconciliation and insert the corporation tax previously paid into Box 595 'Tax already paid(and not already repaid)'
  3. Go to Overpayments and repayments, then complete this section as appropriate
  4. Go to Finalising the return and tick the box for 'this return period?'
  5. If you want to add any notes (that would usually be covered in an additional information box): Please go to Computation Management > Edit Notes > Select the location where you want to place the information save this as required
  6. Re-submit a full return for a refund of the difference in Corporation Tax – for instructions on how to submit an amended return please see the following knowledge-based article: How do I resubmit a return or file an amended return?

Entries to make for the previous year return period(s) in which loss relief is being claimed: Return period starting prior to 01/04/15

HMRC Forms mode (Version 2)

  1. Go to CT600 > Computations > Trading losses record
  2. Insert the loss figure into the box labelled "Trading losses of a later accounting period utilised"
  3. Go to CT600 Full/Short > Page 1 and tick the box for "A repayment is due for this return period"
  4. Then go to
    1. Full > Page 5 > Complete box 91
    2. Short > Page 3 > Complete box 91
  5. Then go to
    1. Full > Page 8 and complete the necessary details
    2. Short > Page 4 and complete the necessary details.
  6. Re-submit a full return for a refund of the difference in Corporation Tax – Please note, this will have to be done via a paper submission.

Simple Step mode (Version 2)

  1. Go to CT600 full/short > Trade and Professional Income > Trading Losses Record
  2. Insert the loss figure into the box labelled "Trading losses of a later accounting period utilised"
  3. Go to Tax reconciliation and insert the corporation tax previously paid into Box 91.
  4. Go to Overpayments and repayments and complete this section, as applicable.
  5. Go to Finalising the return and tick the box for "this return period?"

Re-submit a full return for a refund of the difference in Corporation Tax – Please note: this will have to be done via a paper submission.  

Alternative to sending an amended paper return if the filing window has closed

If the window for amendment of the previous return has closed, (In excess of 12 months after the filing deadline) you can write to your company's Corporation Tax office including the below:

  • The name of your company or organisation
  • The period when the loss is made
  • The amount of the loss
  • How the loss is to be used

For further information, please the HMRC claiming a loss.

Article ID: 828
Last updated: 29 Apr, 2021
Revision: 11
Views: 27926
This article was:  


Also read
item How do I resubmit a return or file an amended return?
item What tax years can I file online?

Also listed in
folder Tax Return Production -> CT600 Corporation Tax Return