If your membership plans expire after a fixed period, you can configure this contract length on the membership plan. You can also configure whether the membership plan should automatically terminate, or renew and what renewal/termination email should be sent to your patients.
To configure contract lengths:
Click on 'Admin' in the upper right menu bar
Click on 'Membership Options'
Click 'view/edit' on the membership plan you would like to add a contract period to
Toggle on 'contract expiration' in the contract periods section
To customize the text on the renewal email:
Click on 'Admin' in the upper right menu bar
Click on 'Notifications'
Click on 'Membership Notifications'
Click 'Customize' next to the renewal email