Maintain books and records of all your Canadian import transactions for a period of six years plus the current year.
Maintain these records in Canada by an appointed customs broker or outside of Canada on the non-residents premises by establishing a letter of undertaking with Canada Revenue Agency and requesting an authorization from the Revenue. A letter of undertaking with CRA commits the non-resident importer to cover the traveling costs for a "Customs Auditor" to conduct an audit at the premises of the NRI.
The NRI will invoice and charge the Canadian customer for the product, duty, tax, and shipping cost. The invoices must state the tax as "Canadian Tax" and show their GST/HST Registration Number on their invoice if they are a GST/HST Registrant.
The NRI will then pay the same applicable duty and tax to their broker to pay Canada Customs on their behalf.
The NRI (if they are a GST/HST Registrant) must file and remit their GST/HST Tax to the Canada Revenue Agency, showing what tax they collected from their Canadian customer and what tax they paid out to their broker . This can be remitted monthly, quarterly or yearly, this is also known as their "Input Tax Credit" (ITC). • Here is a guide for GST/HST for Registrants General Information for GST/HST