HMRC letter codes · One-to-many letters
CTL24MMLetter about differences in the loss position of Company Tax Returns
Published by its source on 23 September 2024. A date in the letter that has passed stays passed: what a passed date means.
Last reviewed 14 October 2026 · How Tax Letters checks its facts
In short
HMRC's letter CTL24MM is headed “Differences in the loss position of Company Tax Returns”.
“CTL24MM … Differences in the loss position of Company Tax Returns”
ICAEW: HMRC letter CTL24MM, as published with its tax news item · checked 14 October 2026
Information, not advice: this page reports what HMRC, GOV.UK and the bodies named publish about CTL24MM. Each fact has its source and the day it was checked beside it.
When HMRC sends it
ICAEW said, in the news item with HMRC's letter CTL24MM, that HMRC was writing to companies and their agents where the amounts for losses reported in the company’s tax return (form CT600) were different from those in the accompanying tax computations.
“HMRC is writing to companies and their agents where the amounts for losses reported in the company’s tax return (form CT600) are different from those included in the accompanying tax computations.”
ICAEW: CT600 loss figures may be incorrect · checked 14 October 2026
What it asks
HMRC's letter CTL24MM asks a reader who disagrees to email [email protected], with the caseflow reference in the subject line.
“What you need to do if you disagree Please send us an email to [email protected] including the caseflow reference at the top of this letter in the subject line of the email.”
ICAEW: HMRC letter CTL24MM, as published with its tax news item · checked 14 October 2026
HMRC's letter CTL24MM says HMRC will use the tax computations, not the CT600 boxes, as the accurate loss amount, and a reader who is happy with that does not need to contact HMRC.
“This means we won’t be using the CT600 boxes shown above. If you’re happy for us to do this, you don’t need to contact us.”
ICAEW: HMRC letter CTL24MM, as published with its tax news item · checked 14 October 2026
Free help and HMRC contacts
HMRC's letter CTL24MM points to the GOV.UK Company Tax Return guide at www.gov.uk/guidance/the-company-tax-return-guide.
“For further information about Company Tax Returns Go to www.gov.uk/guidance/the-company-tax-return-guide”
ICAEW: HMRC letter CTL24MM, as published with its tax news item · checked 14 October 2026
Free help first
These routes are described by GOV.UK, TaxAid and Citizens Advice themselves.
- HMRC's extra supportHMRC offers extra support if your health condition or personal circumstances make it difficult to contact HMRC, for example a mental health condition, financial hardship or being treated in hospital.
- Someone to deal with HMRC for youYou can authorise a friend, relative or voluntary organisation to talk to HMRC for you and help you fill in forms.
- TaxAidTaxAid helps people with tax problems who cannot pay for advice. Tax Help for Older People merged with TaxAid in July 2025.
- Citizens AdviceCitizens Advice gives confidential advice online, over the phone and in person, for free.
- ICAEW: HMRC letter CTL24MM, as published with its tax news item (checked 14 Oct 2026)
- ICAEW: CT600 loss figures may be incorrect (checked 14 Oct 2026)
- GOV.UK: Get help from HMRC if you need extra support (checked 7 Oct 2026)
- GOV.UK: Appoint someone to deal with HMRC on your behalf (checked 7 Oct 2026)
- TaxAid: About us (checked 8 Oct 2026)
- Citizens Advice: About us (checked 7 Oct 2026)