A more thorough explanation:

Definition: To put a later date on a document than the actual date.

Example: If you write a check on January 1st but put a date of January 15th on it, you have postdated the check.

Explanation: Postdating is when you write a date on a document that is later than the actual date. This is often done with checks to delay the payment until a later date. In the example given, the check was written on January 1st but postdated for January 15th, meaning the recipient cannot cash the check until that later date.