WSIB pays Harmonized Sales Tax (HST) Effective July 1, 2010, the WSIB is required to pay the new Harmonized Sales Tax (HST). Pre-billing for services that will be provided beyond June 30 must reflect the different GST/HST provisions before and after July 1. It is the responsibility of the vendors, suppliers and service providers to determine which of their goods or services are subject to HST.