Extend Child Benefit for your teen before 31 August.
Parents of 16 to 19-year-olds entering further education or approved training must notify HMRC to extend their Child Benefit claim. This action must be completed by 31 August to prevent payments from stopping automatically. You can update your claim online via GOV.UK or the HMRC app.
Source: https://www.gov.uk/government/news/extend-child-benefit-for-your-teen-before-31-august. Summarised automatically from the official source — general information, not advice.