Toronto is the largest city in Canada. As the United States single largest trading partner, it is likely that if your business deals in shipping to international clients at least some of them will be in Canada, and if you're shipping to Canada at all then that likely means you're shipping to Toronto. If a company is shipping to Toronto for the first time, they may have questions about the kinds of fees and surcharges that they may be looking at for a Toronto delivery, both government taxes and fees, as well as those that may be charged by the courier.
A Toronto courier company of any kind would be able to explain fully these charges, taxes, and fees, but the basic rundown is that you will have to pay the GST, and because Toronto is in Ontario which has a PST, that tax as well. Not all Canadian provinces have a provincial sales tax, so that tax and its amount will depend on the province you are shipping to, the GST on the hand is nationwide. These taxes will be applied after any customs duties are assessed.
If your delivery or shipment is originating in the United States, (or any other country) then it will have to pass through customs before it reaches Toronto. Your Toronto delivery may be subject to a duty fee depending on what it is you're shipping. In order to determine whether or not you're going to have to pay duty, you should consult with your courier about your shipment. They will be able to tell you exactly what kinds of duty fees are in place for your particular types of goods. The only other way to find out is to wait until your goods are at the border to see how much it is going to cost you to move them across.
The final fee that you're going to have to contend with is a fee charged by the courier company, delivery company, or postal service that you're using to transport the goods across the border. This brokerage fee is usually a single charge assessed to a single shipment. A good money saving tip is to try and consolidate small shipments into a single load in order to help you to save on the brokerage fees. That way, you're only going to end up paying the brokerage fee on a single shipment instead of every time you need to send something across the border.