During the sign-up process, you’ll be asked your date of birth to make sure that you’re not a minor. Once you’ve accumulated some winnings and you’re ready to request a withdrawal, you’ll be asked to upload proof of identity such as driver’s license, utility bills, passport, etc. Only when the online casino is sure that you are who you claim to be, will the money be released. Online casinos will invalidate any claims if it’s found that you are a minor.