How Can /purchases-invoices Be Queried by contact_name?

In Sage Business Cloud Accounting, you cannot query by the field 'contact_name' directly; you can only query by contact (contact ID), status, search, from_date, and to_date.

For example to query for a specific contact named "ABC Distributing" you need to structure your Where clause query using the word 'search' such as where: search='ABC Distributing'.

More:

https://developer.sage.com/api/accounting/guides/invoicing/