Originally posted by PentaPrime if I arrange a shipment within the US, pay no tax at time of purchase, and B&H collects no GST, would I only pay it if I declare at the border?
If you declare those goods when you return to Canada and the value is less than your personal exemption, you don't have to pay GST. It doesn't matter if the goods are new or used, it only matters if the actual total value (not what your receipt says) of all declared items is less than your personal exemption. If you entered the U.S. with a bag full of your own used camera equipment and you came back with an extra used lens and you forgot to declare it, you probably won't get asked to prove that you owned all of your equipment before you left Canada, but you are breaking the law.
Since B&H doesn't have a physical presence outside of NYC, they probably aren't collecting local sales tax outside of New York State, but I don't know that for sure and in the near future, B&H will have to collect sales tax on all sales within the U.S. If you order something from B&H to be shipped to Canada, they give you the option of having them remit GST or you can pay the shipping company (Canada Post or FedEx) yourself when you receive the order. On my last B&H order, the fee for remitting GST and customs brokerage was less than $20 Canadian, which is a real bargain.