Hi @sme
With “General Purchases”, I wouldn’t necessarily worry about linking a customers invoice to the suppliers invoice in terms of using the same nominal. As General Purchases (5000) is a Cost of Sales code (5000-5999), it’s generally accepted that these were used to general the sales invoices (in the 4000-4999 nominal code range). Have you been advised any different to this?
However, we completely understand that sometimes you wish to link them for reporting purposes which is why we introduced the project tagging. This would allow you to link both invoices to a tag so you can see profit and loss for that particular “project” for example (I put project in quotation marks because the tags are flexible enough to be used for more than just projects).
You may wish to check out the follow guide, which may help: