Ok a Use case to help demonstrate would be: 1. A new contact in extra is created. 2. They pay for service on Extra. 3. Upon Payment we contact BHQ with new customer creation and new invoice and payment at once. 4 We are happy with this
When you create an Invoice using the API, the response will have a clientId field in it. You can use this ID to get information on the Client using the API for clients. Have a look at the Create call for Invoices (https://www.bullethq.com/api-ireland/v1/invoices) to see an example of how the client id is returned when you create an invoice. Getting/Updating information about the client can be done using this id, see the APIs at https://www.bullethq.com/api-ireland/v1/clients
Yes - You can use the invoice update API and set a different clientName/clientId for the Invoice. But this will remove the link between the previous client and the invoice - an invoice can only be linked to a single client.