If a client wants to pay 1 month or several months in advance, you can choose the option to generate the next invoice. You can generate an invoice in the contract of the client. Through the Clients and Staff module, you can select the clients' profile and choose the 'Products' tab, and click on the membership.
Once you're in the contract of the client, from the Options drop-down select "Generate next invoice".
Tags: bill, create, advance, overtaking, pay