Atheism is the default position. We are all born and remain atheist until the time when we adopt an alternative viewpoint.
Atheism, in the most essential basic meaning of the term is nothing more that the lack of a belief in a deity or deities; a-without, theism - belief in a deity or deities.
Atheism in itself implies neither a religious persuasion nor the lack of a religion persuasion if within the context of religion such is possible without the belief in a deity.
That being said, if I were asked to fill out such a form without so much as the option of "none" or "none of the above" or "none of your ******* business", I would tear up the form, toss it into the nearest bin and walk out the door relieved that I had not consigned myself to working for such inconsiderate devious idiots, although in a world in which such are the norm rather than the exception, such a choice may not necessarily be an option given your current circumstances.
Good Luck