To de-register a youth player you need youth registrar role.
Most registration functionality (including age-grade de-registration) is managed in the v12 registration module.
Go to the V12 Registration Module
I find I have to log in again, not sure if that’s a cookie issue or a system wide issue.
This will take you to the V12 home screen, from which you can select Club/Player management to manage existing registrations.
Search for the payer you wish to de-register (you will need to click the search button, not just type and hit-return)
Select the player using the checkbox and click ‘De-register Selected Player’. You will be prompted to confirm.
Once you have finished – to return to the main GMS system, I find the only way is to retype gms.englandrugby.com/gms into the browser address bar.
This will tell you that your session has expired, and prompt you to re-login. Sometimes you have to re-login twice – who knows why!