To use a date later than the one on which a document is being written. For example, a postdated check which can't be deposited or cashed until the date shown on it.

In banking, postdated refers to cheques which have been written by the maker for a date in the future. Postdated items are described in Article 3, Section 113 of the Uniform Commercial Code. Postdated cheques are often used in conjunction with payday loans.