In most cases, yes, it is necessary to have an account to make a minimum deposit at an online casino. This is because the account is usually used to store the funds and to track your activity and bonuses. However, some online casinos offer a guest checkout option where you can make a deposit without creating an account, but this option may not always be available for minimum deposits. It's best to check with the specific online casino to see if they allow minimum deposits without an account.