Upvote:3
There is no specific rule, rather, you shouldn't be trying to live in the US by successive visits. If you visit the US for five months, leave for three weeks, and then try to return it is likely that the border guard will consider that you are trying to immigrate by default and deny you entry.
I'm not saying this can't be done, but you're going to need an extremely compelling story on your second visit.
Upvote:8
US immigration law generally allows people entering in B-1 or B-2 status (which includes Canadian visitors without visas) to enter for up to six months per visit. There is a lot of misinformation out there about this.
Rather than having a strict requirement of no more than six months out of some longer time period, the US gives immigration officers the discretion to refuse entry, or sometimes to grant admission for a shorter period than six months, if they find that a visitor does not satisfy the conditions of admission as a visitor (for example, if they think you're actually living in the US and making occasional visa runs to Canada).
Canadians (and others) who spend a lot of time in the US also have to worry about US tax law, because spending more than a certain amount of time in the US makes one a US resident for income tax purposes (regardless of immigration status). Such a person must report their entire worldwide income and figure their income tax accordingly.
The answer to your question, therefore, is yes, you can do this, if the officer allows you to re-enter. If the time between your visits is very short, because the officer might decide to consider the length of the two visits together.
In any event, do pay attention to the substantial presence test and the closer connection exception.