I'm a US citizen who has moved to Canada; but the business I own
(doing software development) still has a mailing address (and bank
account) in the US.  I am the sole proprietor; there are no other
employees.  I recently moved my servers from the US to here in Canada.
I do all of my work for US clients remotely.  Is this a legal state of
affairs for a US company?  Do I need to have more of a business
presence in the US than a PO box?  Ideally, I'd like to know what
steps I should take- such as put a US employee in an office space?
Please provide references.  Thanks.

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Clarification of Question by googleda-ga on 25 Mar 2004 12:08 PST

I'm adding this for posterity in case somebody comes across the
question while searching.  I spoke with an accountant; I don't even
need to keep a US mailing address.

The business was started in the US; it will always be a US business. 
There's a concept of "nexus in new york" that means it has to file
there.

An interesting question for me is whether I can file for "foreign tax
exclusion" for US income.  Up to 80K can be non-taxed if I have a US job.

This is different from (and exclusive of) the foreign tax credit.

Anyway.