I work for a contracting company in a contract-to-hire position where I have almost no contact with the contracting company- I send them time cards, and they send me checks. Today I was offered a position at the client company which I accepted, and I gave the contracting company two weeks notice of my resignation.
To be clear, I am an at will employee of the contracting company. The client company has offered me a position, which I have accepted. There are no contractual barriers to my accepting this position.
All of the reasons I know of to offer a notice period to the contracting company do not apply- they have no work for me to handoff or complete, they will not need to replace me, and there is no transition plan to make and execute. The only difference I see in offering a notice period is that they continue to collect their margin for two weeks longer.
Would it have been unprofessional to resign from the contracting position without any notice at all? If so, why?