Thousands of parents are being warned to update their child benefit details to avoid losing up to £1,067 a year from this month.
HMRC said parents will need to tell the tax authority if their child is staying on in education after picking up their Higher results earlier this month.
Failure to do so could mean their payments are stopped on August 31 - costing some families more than £1,000 a year.
Young people are still eligible for the benefit, worth up to £20.70 a week, after they turn 16 if they're continuing in education .
However parents and guardians will only continue to receive it if they tell HMRC before the cut-off, when payments will automatically be ceased.
Angela MacDonald, at HMRC said: "As parents and students look forward to results day, we're encouraging them to meet the August 31 deadline and notify us of their children's plans. Letting HMRC know will ensure that Child Benefit payments continue."
You can claim child benefit if you're 'responsible for a child' that's under 16 - or aged 16 to 20 and still in education or training.
Claimants can get £20.70 a week for their eldest or only child, and £13.70 a week for each additional child, up to the age of 19 for those on approved courses or training.
This includes those studying for A Levels, Scottish Highers, International Baccalaureate, NVQs and other vocational qualifications up to level 3.
Training courses should be unpaid and can include Employability Fund programmes in Scotland.
You can update your details online here or by contacting HMRC directly get in touch by phone, call 0300 200 3100, lines are open Monday to Friday 8am to 8pm and Saturday 8am to 4pm.
Parents and guardians should note that if they or their live-in partner has an individual income of over £50,000, they may have to pay a tax charge, known as the High Income Child Benefit Charge.
