US business people visiting Canada need proof: You probably already know this. This news is from Thomson Reuters.

This is good information

U.S. passport holders must now have specific documentation from their company when traveling to Canada on business. While this policy is not entirely new, the Canadian Border Service Agency is now strictly enforcing this requirement. For further details, click here.
Documents needed at the Canadian border
The Canadian Border Service Agency may deny entry for not having the below requirements:

• Passport or travel document that is valid for your entire stay and guarantees re-entry to your country of origin.
• Valid temporary resident visa, if applicable.
• Letter of support from your U.S. based company, on company letterhead, stating the purpose of your visit to Canada, the duration of your stay and the name, address and phone number (24 hour contact) of the Canadian contact(s) you are visiting. To view a sample letter, click here.
• Other documents relevant to the visit, e.g., contracts, warranty or service agreements.
• Proof that you have enough money for both your stay in Canada and your return home.

Please Note: As per the Canadian Border Service Agency, it is recommended, though not required by law, that a letter with the above information be included from the Canadian company with whom the traveler is doing business.