What are the rules for foreign based consultants?

[zinneken]

I'm a foreign based consultant, with a potential client in Canada. I'd like to find out what the rules are for consultants offering consulting work in Canada to Canadian companies.

Which are the rules governing foreign based consultants who have an assignment in Canada for a Canadian company?

How/where can I find out if for this one-off 4 week production improvement and optimisation project I need immigration documents or not?

Thanks!