Is there a way to achieve this without scripting? Facts: I have a header Class field on the Invoice that is automatically populated. Each item is tagged to an Item Category in the item record. I have a custom record with Class, Item Category and Basis % as fields. Goal: When the invoice is created, I want to automatically source the Basis % from that custom record to a custom invoice line field based on the Class and item category without manually selecting the custom record in the invoice. In a workflow, I can probably build a lot of set field value actions but I'm trying to avoid that either, so I won't need to add more set field value actions when there is a new class or item category.

not sure you can do this without scripting But why you don’t put the basis on item directly ? 1 item = 1 class = 1 basis ?

Cannot be in the item directly because the Class affects the Basis %. For example, Class A + Item A has a different Basis % from Class B + Item A (same item but different Class)