Finding Voucher Number on TAP Transaction Created From AP

If it is a paid voucher, one way to find it would be to look in Matter Status and double click on the TAP on the A/R Ledger Tab and look at the check #.   Go to Accounts Payable Manager and to Action > Account Status, put in Firm as the vendor, look on the Checks tab and find the check number listed. Drill down into the check and see the vouchers listed with the voucher number. 

Another way would be to run a Voucher Listing report.  An alternative in would be to filter in AP Manager using the appropriate criteria, if needed sort by firm name as vendor, and look for it based on the amount in question.