"Postdated" means writing a date on a document that is later than the current date. It is often used for cheques or contracts to indicate that they should not be cashed or implemented until the specified date arrives. Full definition
@SaultDon: That still doesn't totally explain why you're giving a bunch of postdated checks at once. (money.stackexchange.com)
Intrapartal mortality during intended home birth is concentrated in postdates pregnancies with evidence of meconium passage. (believemidwiferyservices.com)
The signing and stamping of the loan agreement happens at this stage where you also provide postdated cheques to your lender and pay the stamp duty as required. (housing.com)