In GP 2013, when a customer payment is voided, any credit associated with that invoice will also be voided. Details at Feature of the Day: Unapply Credit Documents when Voiding a Check
Feature of the Day: Unapply Credit Documents when Voiding a Check – Inside Microsoft Dynamics GP – Site Home – MSDN Blogs
Payables & ReceivablesTips & Hidden FeaturesMicrosoft & the GP EcosystemGP 2013
Archived post from 2012. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.