The GST return is a calculation in the difference as to how much GST has been collected versus paid out in a particular reporting period. All businesses with taxable sales in excess of $30,000.00 a year must register and charge GST. Businesses with taxable sales under $30,000.00 may elect to register for GST as a small supplier. GST is generally charged on all products and services however due to the complexity and nature of the excise tax act there are many exceptions to this rule. For example, certain goods and services are exempt from GST while other are defined as zero rated. This is an important distinction because of how input tax credits are claimed.