Once a voucher has a payment but it was voided, can the voucher be cancelled or closed?

My issue is we have a voucher for a po that is using a contract.  The payment was voided and those vouchers no longer need to be paid.  However, I cannot reduce my po down (and there by putting the money back on the contract) because the voucher exists.

Can a voucher with a voided payment be cancelled or deleted?