Malcolm, I don't think there is any problem with a credit card company charging a commission on the sales tax portion of an invoice. It goes on everytime you use your credit card to buy something....
Example, when you go into a store and buy an item, the clerk rings it up, taxes are added and you give the clerk your credit card. They swipe it through and punch in the value of the sale including taxes and the credit card company charges you the total amount of the sale and transfers the same value to the retailers bank account. Now when the credit card company calculates the discount rate applied, it is on the total value of money transferred, not just the value of the goods less sales taxes.... So Canadian Credit Card operators have been gaining commissions on the value of sales taxes collected on retail and other sales for years.....
Glenda, probably 95% of our sales are settled via Paypal. I always send an electronic invoice and in the freight field, I include the charge for freight, plus GST and applicable Provincial Sales taxes, and then in the note section I give a break down explaining $14.98 as shown as Canada Post is $8.50 Canada Post, 2.98 PST and $3.50 GST as an example.
From time to time I will have someone email back saying freight is extrodinarily high, but this us usually due to them not reading the entire invoice and not the note. When I bring this to their attention they are fully aware and have never had a problem.
Not to say that from time to time I don't have people as we all do who don't think they should be paying taxes on an Ebay purchase, but then I point out that our tax policy is clearing indicated on the listing and they should not bid or buy if they are not willing to pay the applicable taxes.
I wish they would update the tax structure on Ebay invoicing, but think about it, I list on the .com site and if they incorporated the ability to show taxes for Canadian sales, wouldn't they have to do the same for every other country in the world that has vendors listing on the .com site?
They should probably update the .ca site to allow for including Canadian taxes in the invoicing system, but honestly I don't use the .ca site.
Jeff