Tue Feb 17, 2009 1:00 pm
You can attend trade shows in the US on B-1, but you can't operate a business there accepting money. You're allowed to enter to accept orders from customers whom you have an existing relationship with, but that doesn't sound like the situation here.
All US-source income is subject to US income taxes, how you file depends on the organization of your business. As a sole proprietor you would use 1040NR and file an 8840 with it (most likely), as a corporation you would use 1120-F and an 8833. Whether you need to do anything else depends on how long you are in the US and whether your business has a "permanent establishment" in the US, which means more than 50% of the work is done there or it is a fixed office or some type.
Basically at some point you have to register for an EIN, do payroll withholding etc. in the US as a US employer would. Depends on the nature of the business to a large extent.
Steve.