Under the rules for GST/HST, the usual method of calculating the net tax to remit involves calculating the tax you collected and your input tax credits, subtracting one from the other, and remitting the net amount.
Some businesses that make more than $400,000 annually in taxable supplies can opt to use the “quick method”. When using this calculation, you only need to know how much tax you collected in the applicable period and apply a percentage to that amount. The resulting calculation is the amount you need to remit. The actual percentage to use varies from province to province but is meant to reflect a reasonable estimate of the result that would be obtained using the regular method. If you choose to use the quick method, you must do so for at least one full year.