I was really taken for a loop on this one! The previous response is about the case. If the item is delivered and it is a hard tub then it is considered real property. Here is a link to read up on.
My experience was that one company was not going to charge me PST. When I finally bought from another company, the process went like this. The final price of the tub was given to me, On a separate pieice of paper both RST(PST) and GST were calculated and added in based on the selling price. These figures where then transferred to the final sales invoice and with the invoice reading as no PST payable and or all taxes included.
The main point here is that RST must not be charged or shown on the invoice to the customer. Using this methodology the requirements have been met by the dealer.
I believe that the Pst is payable by the dealer on their cost of the tub and on any other materials which become part of the real property.
If you want to get technical one might argue that you are being overcharged PSt on the dealer markup. However if the invoice is written up as above, which they all probably are, then you don't have a leg to stand on. T
http://www.rev.gov.on.ca/english/notices/rst/43.html
Good luck, Let us know how you make out!