This article shares a possible use case your app could support, as well as a sample flow that could support the use case. You aren't limited to these exact flows, but it can be a helpful jumping off point as you plan your app's implementation.
A business operating in the United Kingdom needs to charge and collect tax at different rates throughout the country. Your app can provide the correct tax to charge for their sales.
Follow these steps to create an app that can calculate tax for the United Kingdom.
Configure the service plugin and give it a calculatorDisplayName, such as "UK Tax App".
Use Tax Regions API to create or update tax regions for the UK with your app ID in the appId field.
Add logic to your app so that when Wix calls it with Calculate Tax your app returns a tax calculation based on different, relevant tax regions in ISO-3166 alpha-2 format.
[Optional] You may also want to offer additional tax rates based on different categories of products. Use the Tax Groups service plugin to configure such tax groups.