Positive and negative vouchers will not net to each other and drop off the aging report.   Manual adjustments will need to be made to both the positive and negative voucher to bring the balance on each voucher to zero.   The same G/L account should be used for the distribution so there will be no impact on the GL.

Negative vouchers are normally the result of a return to the vendor and credit received.   The credit should be processed through Debit Return in Purchase Order Receivng, and an Adjustment Voucher should be created in Generate A/P Transactions.