Client is for a Canadian Firm at US site

I would like to know if a Canadian Citizen, working for a Canadian consulting firm could work on a mandate at a USA site belonging to a Canadian company.

For example, 12345 Canada inc is given a contract by a Canadian Bank to install security cameras in their US branches. Can 12345 Canada inc send their Canadian employees ?

They could do, as long as they have some kind of a work permit/status, such as TN (for any job titles as specified by NAFTA) or L-visa (for transfer employees, employed with the company for at least one year)

No Canadian citizen may work in the USA unless he/she is legally allowed to do so. Just as no US citizen may work in Canada without without being legally allowed

If you're asking for yourself, and would work at the US branch as a consultant, then you're in luck because consultants qualify for TN status. However, it is also a highly scrutinized title due to abuse and misrepresentation. If you're really a consultant with the proper background and can prove it, then it shouldn't be a problem at all. TN's are easy enough to obtain at any port of entry. The TN letter would have to be written by the US branch though. Not your Canadian office. That is my understanding anyway.

Try and do a search for consultant on this board, I'm sure a lot of information will pop up.

Hope this helps!

Yes they can, installations are permitted as a regular B-1 visitor for business under NAFTA, you don't need any additional work authorization. Be sure you have the relevant documentation, e.g. a sales invoice from your company with the US purchaser's details on it.

Do a search on the web for "B-1 NAFTA entry" and read the regulations. Note that is must be a company outside the US to qualify for most of exemptions, you can't enter as a visitor to work for a US company except in rare situations such as some transportation jobs.

Note that if the employees earn more than $10,000 while in the US (you can't fiddle it, whatever they are ordinarily paid, say they work hourly doing the installations and the total amount paid during the year is over $10,000) then the Canadian company must have a US payroll, EIN, file an 1120-F, perform US payroll withholding etc. and issue all Canadian employees who work in the US W-2s. Those employees must file a 1040NR in the US every year and claim a foreign tax credit on their T1.

More involved cross border work might require sponsorship, for example if you have a US office then you can transfer workers there who have "specialized knowledge" either under L-1B (which is valid up to five years) or if they're in the US less than 183 days a year as L-1 intermittent (which can be renewed indefinitely). The US office has to file an I-129 with USCIS to sponsor them.