Inventory Invoices

I'm trying to build a system to keep track of inventory for a restaurant. It is to replace an older DOS style one that only shows results after a count (it calculates everything by a batch process).

Anyway one headache for users is entering many incoming product invoices. Ingredientinvoices to be more specific. Our current system has a layout with a list to chose items assigned to that vendor. I would like to add reoccuring sample invoices and purchase orders that can be made up as a work sheet but may or may not be used.

I'm wondering if I should keep these types of things in the invoice/line item tables with a marker field or put them in completely different table(s) and have them copied in if they actually become invoices.

Of course, one day I'll want the system to create its own suggested invoices not based on par order amounts but on previous average usage.