If the new order is for a subscription, the expiry date of the subscription will be automatically set to today's date plus the length of the subscription.
For example, if the subscription is quarterly and the date today is 03/04/2021, then the expiry date of the subscription will be set to 03/07/2021, which is 3 months ahead.
You can change the subscription's expiry date via the 'subscriptions' tab on the contact's record cart.
A renewal invoice will be automatically sent to the client a month before the expiry date. This only happens if there are no older unpaid invoices for the same subscription as it is assumed that, if a client has not paid to renew previously, there isn't much point sending a new invoice for the same subscription.
The client can pay via the 'my account' section on your website or your can manually process a payment via the BMS. To do so, simply open the order/invoice and add the payment in the 'transactions' section.
Important: If the payment is for a new subscription you have created (i.e. it is not to pay for a renewal), paying the invoice will not alter the expiry date of the subscription, it will remain as it was set when you created the new order. It is only when a renewal invoice is paid that the expiry date is changed to a new date in the future.
Related info: when a full payment is made to renew an existing subscription (i.e. it is not a new order), a new expiry date is set based on the old expiry date plus a period equal to the subscription period. For example, if a quarterly subscription expiring on 03/06/2021 is renewed (invoice paid in full), a new expiry date for this subscription is set to 03/09/2021.