There is no easy way in Dynamics GP to see what check or credit memo was applied to a particular Purchase Order. If you have SmartList Builder, you can easily incorporate this SQL view into a new SmartList:
create view view_WhatCheckPaidMyPO
as
/** view_WhatCheckPaidMyPO
Created on 10/17/2008 by Victoria Yudin, Flexible Solutions, Inc.
For updates see http://victoriayudin.com/gp-reports/
Does not take Multicurrency [...]