You can sell a product up as a recurrent sale, which means it will be invoiced at specified intervals to customers.
Examples of items you may want to sell as recurrent products include parking passes or locker rentals. To allow a product to be purchased on a recurrent basis, open the advanced options for the product. In the Available as section, ensure Both as recurrent as a one-off purchase or Only as recurrent is selected.
In contrast to a contract, which makes a customer a member, selling a recurrent product will not make a customer into a member. Even though this customer will be invoiced for that product automatically based on the billing cycle you set when selling the recurrent product, they do not have a contract and are not a member.
For example, you may have:
A customer who purchases 5 day passes every month, so they always have a valid pass for days they want to check into your location.
A customer who purchases 10 days passes every 3 months because they are only in town for several days per quarter.