How do I "undo" or reverse a payment to a vendor?

I have made a payment to a vendor, but entered an incorrect date, far in
the future. Consequently the payment does not show when I try to reconcile
the relevant bank statement.

How do I back-out the incorrectly entered payment?

Cash/Vouchers/Reverse Payment.

Then when you are done adding the payments you want to reverse,
approve the batch.

Tested on: LedgerSMB 1.3.15.
source: http://permalink.gmane.org/gmane.comp.finance.ledger.smb.user/6087