Real Dictionary

postdate in Accounting
verb: If you postdate a check or other document, you put a future date on it so that it is not valid until then.

postdate in American English
to assign a later date to than the actual or current date
transitive verb: to date (a check, invoice, letter, document) with a date later than the actual date

postdate in British English
to write a future date on (a document), as on a cheque to prevent it being paid until then

postdate in Finance
verb: If you postdate a check or other document, you put a future date on it so that it is not valid until then.