HMRC letter codes · Child Benefit (CH)
CH105Allow someone to help you with your Child Benefit
Last reviewed 14 October 2026 · How Tax Letters checks its facts
In short
GOV.UK says to use form CH105 if you want an intermediary, such as Citizens Advice, to help you with your Child Benefit.
“Use form CH105 if you want an intermediary, such as Citizens Advice, to help you with your Child Benefit.”
GOV.UK: Child Benefit: allow someone to help you with your award (CH105) · checked 14 October 2026
Information, not advice: this page reports what HMRC, GOV.UK and the bodies named publish about CH105. Each fact has its source and the day it was checked beside it.
What it is
GOV.UK's guide says a partner or someone else can get general advice from the helpline but must be authorised to discuss a claim, and that the claimant gets them authorised with form CH105.
“A partner or someone else can get general advice but they must be ‘authorised’ to discuss a claim with the helpline. … The claimant must fill in form CH105”
GOV.UK: Claim and deal with Child Benefit for someone else · checked 14 October 2026
What it asks
GOV.UK's guide says the claimant must fill in form CH105 and send it to the Child Benefit Office, and that the address is on the form.
“The claimant must fill in form CH105 … send it to the Child Benefit Office - the address is on the form.”
GOV.UK: Claim and deal with Child Benefit for someone else · checked 14 October 2026
GOV.UK's guide says the claimant can write a letter with the same information instead of filling in form CH105.
“The claimant must fill in form CH105, or write a letter with the same information”
GOV.UK: Claim and deal with Child Benefit for someone else · checked 14 October 2026
Time limits and rules
GOV.UK's guide says an authorisation made with CH105 lasts 12 months unless a different end date is put on the form.
“The authorisation lasts 12 months unless a different end date is put on the form.”
GOV.UK: Claim and deal with Child Benefit for someone else · checked 14 October 2026
Free help and HMRC contacts
If you cannot find the answer in the official HMRC app, GOV.UK says to call HMRC on 0300 200 3100 with a question about Child Benefit, including one about a CH105 authorisation. Lines are open Monday to Friday, 8am to 6pm, closed bank holidays, and GOV.UK links to its call charges page.
“Call HMRC if you have a question about Child Benefit and you cannot find an answer in the official HMRC app. … Telephone: 0300 200 3100 … Opening times: Monday to Friday, 8am to 6pm. Closed bank holidays. … Find out about call charges”
GOV.UK: Child Benefit: enquiries · 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.
- GOV.UK: Child Benefit: allow someone to help you with your award (CH105) (checked 14 Oct 2026)
- GOV.UK: Claim and deal with Child Benefit for someone else (checked 14 Oct 2026)
- GOV.UK: Child Benefit: enquiries (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)