TinyTax doesn't currently support loss carry-back claims — CT600 Box 860 (trading losses carried back) isn't available in the TinyTax form.
What TinyTax does handle: filing your CT600 for the current loss-making year (with £0 tax due), and carrying losses forward automatically to offset future profits.
To make a carry-back claim, you have three options:
1. Commercial CT600 software (such as TaxCalc, IRIS, or CCH) — open or create the prior year's CT600, enter the carry-back amount in Box 860, and submit the amended return to HMRC.
2. Paper CT600 amendment — download the CT600 form from HMRC's website, complete it for the prior profitable year with the carry-back amount in Box 860, mark Box 40 as an amendment, and post to HMRC. Note: HMRC's Corporation Tax Online Service closed in March 2026, so direct online submission isn't available.
3. An accountant — can prepare and submit the claim on your behalf using commercial software.
Key points to note:
- You must make the claim within 2 years of the end of the loss-making period
- Losses can only be carried back 12 months (one accounting period)
- You can still file your current year's CT600 through TinyTax showing the loss — the carry-back claim is a separate process that adjusts the prior year's tax position
For full details including terminal loss relief (for companies that have ceased trading), see: https://tinytax.co.uk/support/loss-carry-back-claims
1 Comment
Log in to comment
What TinyTax does handle: filing your CT600 for the current loss-making year (with £0 tax due), and carrying losses forward automatically to offset future profits.
To make a carry-back claim, you have three options:
1. Commercial CT600 software (such as TaxCalc, IRIS, or CCH) — open or create the prior year's CT600, enter the carry-back amount in Box 860, and submit the amended return to HMRC.
2. Paper CT600 amendment — download the CT600 form from HMRC's website, complete it for the prior profitable year with the carry-back amount in Box 860, mark Box 40 as an amendment, and post to HMRC. Note: HMRC's Corporation Tax Online Service closed in March 2026, so direct online submission isn't available.
3. An accountant — can prepare and submit the claim on your behalf using commercial software.
Key points to note:
- You must make the claim within 2 years of the end of the loss-making period
- Losses can only be carried back 12 months (one accounting period)
- You can still file your current year's CT600 through TinyTax showing the loss — the carry-back claim is a separate process that adjusts the prior year's tax position
For full details including terminal loss relief (for companies that have ceased trading), see: https://tinytax.co.uk/support/loss-carry-back-claims