I also learned that there is something called a dormancy fee or maintenance charges on those inactive accounts which covers for administrative cost incurred by those accounts. I learned that the deduction is from the remaining balance in the account. What about inactive accounts without any balance? On the other hand, what type of fee is charged on an active account?
As far as I know, casinos usually deduct it directly from your remaining balance. If the balance is not enough, they may send you a notification requesting to add more money to your account. If you skip adding more money, your account will be permanently canceled or they may deduct your money when you deposit money back into that account again.
If your account is linked to payment methods such as credit cards or cryptocurrency wallets, they can deduct fees from there even if your casino account has no money left.