IDEA: Ask for AP statements from your vendors on a regular basis. They may owe YOU money.

Request all your vendors to send an open detailed statement of all invoices they show outstanding and unpaid of a regular basis. Ask this to be sent every month or two. Those listings that you receive will always be behind.  They may still have items you paid with a check a few days (check not yet received), new invoices (not yet received) or credits (unrecorded because they did not send them to you) which is a pleasant surprise.  There also may be debit memos (charges) back to you for a price, quantity or quality reason. You want to discover and convey all information given to you about debits to your buyer in purchasing. These problems need to be conveyed to your production personnel and quality control department. Statements verify you have all charges plus uncover unknown credits that you need to take asap on the next AP check to be issued.