voucher (n.)

• acceptance
• acknowledgment
• acquittance
• advocacy
• affidavit
• attestant
• attestation
• attestator
• attester
• authority
• authorization
• bill
• bystander
• certificate
• certification
• character
• check
• checkbook
• cheque
• credential
• debenture
• deponent
• deposition
• diploma
• discharge
• draft
• eyewitness
• informant
• informer
• note
• paper
• passerby
• patronage
• quittance
• receipt
• recommendation
• reference
• release
• sheepskin
• spectator
• swearer
• testifier
• testimonial
• ticket
• visa
• vise
• warrant
• warranty
• witness