Tens of thousands of teenagers could be missing out on unclaimed savings worth an average of £2,100.
The money is sitting in untouched Child Trust Funds.
Child Trust Funds were offered to children born between September 1, 2002 and January 2, 2011, having been launched by Labour in 2005.
Each child received a voucher worth £250, or £500 for those from lower income families.
Families could then add up to £9,000 a year, with the child able to access the money when they turn 18.
If the parent failed to open a Child Trust Fund within a year of receiving a voucher, HMRC would have opened an account on behalf of the child.
This means many accounts have been forgotten about and are lying dormant.
The Savings and Investment Alliance estimates more than a quarter of accounts that reached maturity at least a year ago are still untouched.
Gavin Oldham, chair and founder of The Share Foundation, last week claimed £1.7billion was sitting in forgotten Child Trust Funds.
Meanwhile, the latest HMRC figures show the average amount of unclaimed cash is worth £2,100.
How to find a lost Child Trust Fund account
If you know the name of your Child Trust Fund provider, you can contact it directly to find out more about your account.
If you've lost track of your account, you can ask HMRC to help you locate it by filling out a form on Gov.uk.
You can ask HMRC to find a Child Trust Fund if you’re a parent or guardian of a child under 18, or if you’re 16 or over and looking for your own account.
You will need your National Insurance number and Government Gateway - this is free to create - to fill out the online form.
Once you've entered the right information, HMRC should tell you the name of the Child Trust Fund provider within three weeks.
You can also request details by post by writing to: Charities, Savings and International 1, HMRC, BX9 1AU.
Try to include as many details as possible, such as the full name, date of birth and address of the account holder, plus their National Insurance number.
Child Trust Fund accounts can no longer be opened, after the scheme stopped in 2011 - but you can continue to pay into existing accounts.
