I'm self-employed in BC, but don't yet have or need my own GST/PST number. When claiming expense receipts, do I enter the subtotal or the total after tax?

No, you do not include the amount of HST/GST on expenses. According to the Government of Canada, You can only apply for a rebate of the GST or HST you paid on expenses that you can deduct on your income tax and benefit return. You must have paid the GST or HST before claiming the rebate. The amount of HST/GST that was paid when purchasing fuel should be recorded separately from the actual cost of the item.  

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