Best approach in Changing Tax default for each item

[jodjim]

We are using PeopleSoft 8.44 for our Requisition/ Purchasing, Accounts Payable, General Ledger and Payroll. In purchasing, our inventory and non-inventory items (services) have tax defaults (rates, non-/taxable). Unfortunately, a lot of these items are either non-taxable or have different rates from the default. So when preparing vouchers, the accounting has to change these defaults to match what's in the invoice. What we want to change the default for each of these items based on the actual paid invoices. To do this, we're thinking of extracting these items from the database, determine the tax paid, trace them back to where the defaults are set up, and come up with a script to effect the changes into the related tables.

I'm barely a month into this job and so far from the Peoplesoft documentation I've read, there are default hierarchies. Also, there are header, lines, distributions, etc. types of tables, which makes it a challenge in tracing an item. I wish to fast track my learning process a bit. So it would be greatly appreciated if there some suggestions/thoughts out there that could be of help.

Thanks a lot