How do I update 1099 amounts?

This reply is assuming that you already have the values in the G/L Control Account as an opening balance, but do not have any Vendor Ledger Entries?

IN A TEST SYSTEM
To create the Open Vendor Ledger Entries you need to do this with the Taxpoint date and Due dates from the Old system, so you would create a Purchase Journal using the entries values from your old system, and validate the fields.

You could create an Excel Import or Dataport run from the Object Designer, setting the Template Name, Batch name and Line Number, on import validate as you would entering a journal line.

Posting Date (Tax Point Date)
Document No.
Vendor No.
Description
Currency Code
Amount (Old System Remaining amount)
External Document No.
Due Date

Clear the GBPG, GPPG, VBPG and VPPG values

Make the Control Account Direct Posting ("Vendor Posting Group" "Payables Accounts")

Set the Bal. Account Type as G/L Account
Set the Bal. Account No. for each line to the "Vendor Posting Group"."Payables Account"

Create any Dimensions or accept the defaults if setup!

Run a test report to check the values match the old system.

When you post the journal a Vendor Ledger Entry will be created, and two G/L Entries per line to the control account which will net to Zero.

HTH

David

Thanks everyone for your comments here.

Just so I am clear the steps to manually add vendor 1099 data from a legacy system into NAV 2009 R2 is below:
1. Create a "Purchase Journal" for the invoices with a balancing account to offset A/P.
2. On the purchase journal lines, confirm the 1099 code and 1099 amount (should be listed as a negative number).
3. Post the purchase journal
4. Create Purchase Credit Memo's for the invoices added in step 1.
5. Make sure the 1099 amount is blank for these credit memos
6. Apply the credit memos to purchase invoices.
7. Run Vendor 1099-MISC report (10112) and the vendor 1099 details will appear properly?

Please advise.

Thanks,
NAV13