When a member signs up for a contract before the first billing day, you can choose to charge the member for the time that elapses between sign-up and their first billing day. This is known as prorating the contract. For example, if they sign up on the 20th of the month, but the default invoicing day on their contract is the 1st, they will be charged for the time between the 20th and the 1st if you prorated the first invoice.
If the side menu is not visible, click .
Click the contract whose details you want to view.
Under the Price section, select Adjust the next invoice...(prorate). Note: Pro-rating a contract won't work unless the plan it's based on has pro-rating enabled.
Click Save changes.