Overview
You can get permission to deal with someone else’s tax credits. The type of permission you need depends on what you want to do.
You can:
contact HM Revenue and Customs (HMRC) about someone else’s claim - as an authorised intermediary
take responsibility for someone else’s tax credit claim when they cannot manage their own affairs - as an appointee
claim tax credits for both your child and their baby
For further information on claiming tax credits for someone else, see GOV.UK's website.