Voucher, receipt (4)
I believe the answer is:
chit
I believe this clue is a double definition.
'voucher' is the first definition.
(I've seen this before)
'receipt' is the second definition.
(I've seen this in another clue)
(Other definitions for chit that I've seen before include "Pert young lady" , "Short note of money owed or received" , "Impudent youngster" , "Voucher; anag. of 6" , "A short written note" .)