Many people have asked us whether to list on Amazon.com or Amazon.ca.
First of all, regarding requirements for registering to sell for either site:
When you register to sell in the U.S. on Amazon.com, you will need to provide a valid credit card, phone number, and tax information. For taxes, you will be required to go through an online step-by-step interview that will determine whether you will need to complete a W-9 form (as a U.S. taxpayer) or a W-8BEN (as a non-U.S. taxpayer). When you register to sell in Canada, on Amazon.ca, you will need to provide a valid credit card, phone number, and tax information.
North America Unified Account - taken from Amazon
In North America, Amazon has simplified managing your business across the United States and Canada marketplaces. The North America Unified Account enables you to create and manage product offers in both the U.S. and Canada. You control what you sell and where you sell from a single seller account interface.
When you sign up to sell on either Amazon.com or Amazon.ca, your seller account is automatically enabled to sell in both marketplaces. You can switch between marketplaces using the marketplace switcher in Seller Central. This allows you to list products and manage orders in each marketplace.
As a Pro Seller, you will only pay subscription fees corresponding to the marketplace where you first registered to sell. For example if you registered to sell on Amazon.com, you will pay the subscription fees for that marketplace. If you decide to sell on Amazon.ca, you will not pay additional subscription fees. However, for all per-item sales, you will pay the fees applicable to the marketplace in which the item was sold.
In order to sell across the U.S. and Canada, you will need to create listings on both Amazon.com and Amazon.ca. Please note that creating offers in the first marketplace where you register (e.g., Amazon.com) and begin selling does not automatically populate offers in the other marketplace (e.g., Amazon.ca); if you want to sell in both marketplaces, you will need to create offers in each marketplace. See the Listing creation section for more details.
Finally, when setting up a North American Unified Account, you’ll need to provide a bank account in one of the countries supported by Amazon. Currently, Amazon supports U.S. and Canadian bank accounts, as well as bank accounts in other countries across the globe. For more details (including a list of supported countries), please see Amazon Currency Converter for Sellers (ACCS).
So in other words, you can create listings on both amazon.com and amazon.ca if you are registered as a North American seller, but you would need to create a listing on each platform for it to appear on the .com and .ca.
Similar to this there is a Pan-European Amazon account as well, which also offers options such as these for selling across various European countries.