HMRC letter codes · One-to-many letters
CompC1MPMMLetter asking a consultant to check Self Assessment returns for consultancy fees
Published by its source on 30 September 2026. 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 CompC1MPMM is headed “Please check your Self Assessment tax returns”.
“CompC1MPMM … Please check your Self Assessment tax returns”
ICAEW: HMRC letter CompC1MPMM, 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 CompC1MPMM. Each fact has its source and the day it was checked beside it.
When HMRC sends it
HMRC's letter CompC1MPMM says HMRC has received information from private healthcare providers that indicates the reader may have received consultancy fees.
“CompC1MPMM … We’ve received information from private healthcare providers that indicates you may have received consultancy fees.”
ICAEW: HMRC letter CompC1MPMM, as published with its tax news item · checked 14 October 2026
ICAEW said that in the campaign that includes HMRC's letter CompC1MPMM, HMRC was writing to individuals it believed might have failed to include consultancy income in their self assessment tax return, based on information received from healthcare providers.
“HMRC is … writing … to individuals who it believes may have failed to include consultancy income in their self assessment tax return, based on information received from healthcare providers.”
ICAEW: Tax news in brief 30 September 2026 · checked 14 October 2026
What it asks
HMRC's letter CompC1MPMM asks the reader to check they have declared all their consultancy income on the relevant Self Assessment tax returns.
“CompC1MPMM … Check you've declared all your consultancy income on the relevant Self Assessment tax returns”
ICAEW: HMRC letter CompC1MPMM, as published with its tax news item · checked 14 October 2026
HMRC's letter CompC1MPMM says that if a return is not correct the reader is asked to amend it.
“CompC1MPMM … If a return isn’t correct, please amend it.”
ICAEW: HMRC letter CompC1MPMM, as published with its tax news item · checked 14 October 2026
Time limits and rules
ICAEW says that the letter of the CompC1MPMM campaign sets a deadline for the individual to respond and explains the consequences of failing to take action.
“The letter sets a deadline for the individual to respond and explains the consequences for the individual of failing to take action.”
ICAEW: Tax news in brief 30 September 2026 · checked 14 October 2026
Free help and HMRC contacts
HMRC's letter CompC1MPMM points to GOV.UK, search “Self Assessment”, then “If you need to change your return”.
“CompC1MPMM … go to GOV.UK search ‘Self Assessment’, and choose ‘If you need to change your return’”
ICAEW: HMRC letter CompC1MPMM, as published with its tax news item · checked 14 October 2026
HMRC's letter CompC1MPMM gives the phone number 0300 123 0998 for a reader who does not think they have income to disclose, to let HMRC know by the date printed on the letter.
“CompC1MPMM … If you don’t think you have income to disclose, please let us know by the above date. You can call us on 0300 123 0998”
ICAEW: HMRC letter CompC1MPMM, 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 CompC1MPMM, as published with its tax news item (checked 14 Oct 2026)
- ICAEW: Tax news in brief 30 September 2026 (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)