Possible Clues:

• Sales slip
• Acknowledgement of a payment
• By the sound of it, sit down again, having paid
• Proof of ownership
• Need for a return, usually
• Acknowledgement of payment
• There's no returning without it
• You may need this to pick up items at the cleaners
• Translator keeping man on board turns in acknowledgement
• It's right to keep a bit back to have something for the auditor