HMRC letter codes · One-to-many letters
MM1aHICBCSALetter asking whether the High Income Child Benefit Charge is due
Published by its source on 20 August 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 MM1aHICBCSA is headed “Check if you need to pay the High Income Child Benefit Charge”.
“MM1aHICBCSA … Check if you need to pay the High Income Child Benefit Charge”
ICAEW: HMRC letter MM1aHICBCSA, 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 MM1aHICBCSA. Each fact has its source and the day it was checked beside it.
When HMRC sends it
HMRC's letter MM1aHICBCSA asks the reader to check whether they need to pay the High Income Child Benefit Charge (HICBC) for the 2022 to 2023 tax year.
“MM1aHICBCSA … We’re asking you to check if you need to pay the High Income Child Benefit Charge (HICBC) for the 2022 to 2023 tax year.”
ICAEW: HMRC letter MM1aHICBCSA, as published with its tax news item · checked 14 October 2026
ICAEW said, in the news item with HMRC's letter MM1aHICBCSA, that HMRC was asking taxpayers to amend their 2022/23 tax return if they should have paid the high income child benefit charge (HICBC) and didn’t, or if they declared the wrong amount.
“HMRC is asking taxpayers to amend their 2022/23 tax return if they should have paid the high income child benefit charge (HICBC) and didn’t, or if they declared the wrong amount.”
ICAEW: Taxpayers should check HICBC for 2022/23 · checked 14 October 2026
What it asks
HMRC's letter MM1aHICBCSA says a reader who has already paid the charge, or has already checked they do not need to pay it, can ignore the letter.
“MM1aHICBCSA … If you’ve already paid the charge, or you’ve already checked you don’t need to pay it, you can ignore this letter.”
ICAEW: HMRC letter MM1aHICBCSA, as published with its tax news item · checked 14 October 2026
Time limits and rules
HMRC's letter MM1aHICBCSA gave 30 September 2024 as the date for the reader to use the information with the letter to check whether to amend their 2022 to 2023 Self Assessment return. That is the date printed on this 2024 letter, and it has passed.
“MM1aHICBCSA … What you need to do by 30 September 2024 Please use the information included with this letter to check if you need to amend your 2022 to 2023 Self Assessment return.”
ICAEW: HMRC letter MM1aHICBCSA, as published with its tax news item · checked 14 October 2026
ICAEW said HMRC's letter MM1aHICBCSA stated that the taxpayer should amend their return by 30 September 2024, the date printed on that 2024 letter, which has passed.
“The letter states that they should amend their return by 30 September 2024.”
ICAEW: Taxpayers should check HICBC for 2022/23 · checked 14 October 2026
Free help and HMRC contacts
HMRC's letter MM1aHICBCSA points to GOV.UK, search “Child Benefit calculator”, for a reader who is the higher earner.
“MM1aHICBCSA … If you’re the higher earner, check if you need to pay the HICBC Go to GOV.UK and search ‘Child Benefit calculator’.”
ICAEW: HMRC letter MM1aHICBCSA, as published with its tax news item · checked 14 October 2026
HMRC's letter MM1aHICBCSA names the GOV.UK page “If you cannot pay your tax bill on time” and the Payment Helpline number 0300 200 3822 for a reader who may have problems paying.
“MM1aHICBCSA … Go to GOV.UK and search ‘If you cannot pay your tax bill on time’. Or phone our Payment Helpline on 0300 200 3822.”
ICAEW: HMRC letter MM1aHICBCSA, 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 MM1aHICBCSA, as published with its tax news item (checked 14 Oct 2026)
- ICAEW: Taxpayers should check HICBC for 2022/23 (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)