Think I'll call my CPA and check. 🙂
Hope you have a good one, most don't have a clue when it comes to the minutiae of provincial sales tax.
From the Retail Sales Tax Act
51. Uncancelled postage stamps and uncancelled revenue stamps valid for the transportation of mail or for revenue purposes in the jurisdiction issuing such stamps, if the consideration for the sale thereof does not exceed the equivalent face value thereof in Canadian funds. R.S.O. 1990, c. R.31, s. 7 (1), par. 51.
A specific exemption exists, your customers don't receive "uncancelled postage" and they probably pay more in "consideration" than the face value.
I'll take half the standard CPA fee for this consultation :^O

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915
- answering Trolls is voluntary, my policy is not to participate.