You must keep a copy of every bill or credit note given to your customers. You must also keep records and supporting documents at your establishment, your residence or any other place we designate for six years following the last year they cover.

Records and supporting documents in electronic or digital format must be kept in intelligible form on the same medium for the same amount of time. You must also take the necessary steps to ensure and maintain their integrity throughout their lifecycle. These documents may be requested during inspections carried out by our inspectors to verify compliance with tax laws. 

The sales recording system (SRS) or server (or both) stores billing data. You must make copies of the billing data, and you must regularly make paper or electronic backup copies of your transaction data.