Odoo introduced IAPs in version 11. The IAP is used to provide recurring services without any complex configurations. Usually, apps purchased from the app store only require a one-time payment from the customer, because they are normal modules and their use won't cost the developer anything. In contrast to this, IAP apps are used to provide services to users, and therefore, they have an operational cost to provide a continuous service. In such cases, it is not possible to provide a service with just the single initial purchase. The service provider needs something that charges the user in a recurring manner, based on usage. Odoo IAP fixes these issues and provides a way to charge based on usage. In this chapter, we will create a small service to provide full book information based on ISBN numbers.