The system will automatically take your renewal payment on the 15th of the billing month. If for any reason this is unsuccessful, you will receive an email notifying you of the attempt which has been made. This allow you to take the appropriate action if required.
This does not mean your subscription has been cancelled if payment has not been successful, on the first attempt on the 15th. A further 8 attempts will be made to take the funds from your account before the account expires.