I'm importing sale orders from an external system and want to create invoices and payments, and have the payments matched to the invoices.

I'm currently able to successfully create invoices and payments and post them. What I don't seem to be able to do is to match them so that invoices are marked as paid by the payments. I've seen numerous examples from earlier versions of Odoo and many seem to create a relationship between invoice and payment when creating the payment.

What is the correct way of doing this? Should a payment be related to an invoice at creation time? If so, which should be created first; invoice or payment?

I've tried tracing through the logic from the JS component that supports matching through the UI, but hit a stumbling block when the code references payment.transaction for which I have no records even though I have created and posted payments. Am I creating payments incorrectly?