Employed by a Canadian company, doing work in USA?

I see that there's a lot of posts on topics similar to this one, but I haven't been able to see a clear answer to the scenario that I am wondering about. Any insight into my question would be greatly appreciated!

Right now I am employed by a small Canadian company, and I do IT type consulting. The majority of our work and projects are completed in Canada, but we do have many customers in the USA. Up to this point, the only reasons I have travelled to the USA for business have been to attend various meetings with customers. From what I understand, that is the exact scenario that a B1 visa is approved for, and I've never had any notable problems at the border over that type of travel.

Recently our company has won a number of contracts where a portion of the work will require on-site activities, system testing, configuration, etc. As far as I understand, since I will actually be performing work for a US company in the USA, I would not qualify for a B1 visa. Realistically this should be something my company will look into and address for me, but I do not trust them to come up with a proper solution. My question is, if, for example, I am going to be in the USA for two weeks doing work, what type of visa/paperwork do I need to be approved for this to be legal?

While we're on the topic, something I am less concerned about, but more curious about, is whether or not it is completely legal to do contract work remotely for a US company, with no visas, etc in place. For example, say a US company mailed 3 boxes of documents to be processed for data entry, with the result of the work being an Excel file which will be emailed to the US company. Aside from perhaps taxes which need to be appropriately filed, are there any legal limitations on performing this kind of work, as a Canadian, for a US corporation?

Any thoughts or advice on either of my questions would be great, although I only really need to know an answer to the first question! Thanks!

B1 is an acceptable status for continued work (maintenance, installation, troubleshooting, etc) on a pre-existing P.O., especially engineering/software -- as long as you remain employed by the Cdn firm.

The employee would carry a letter from the US entity stating that "Mr x is a Cdn citizen, performing x,y,z for a period abc, during which time he will continue to be employed by CanCo".

I've brought at least 25 people down like this over the past decade without any issue.

As to working in canada for US firm there is no immigration issue here -- you are a Cdn working in canada. so can do what you want. Even taxes would only be an issue depending how you were paid.

Thanks for the reply! does this still apply when no "product" was sold to an american company, service work is simply being done? the work is more along the lines of assessing and testing current network configurations and software installations to determine if any improvements can be made.

I checked more into the B1 visa, and the situation you reference appears to be specific to services bundled with a product which has been sold, as opposed to just completely independent services.

What you describe would not be B1 eligible in my opinion.