How to file the US tax return, what is the form to fill {for foreigners} ?
Form 1040-NR.
Before you can file a tax return, you'll need to obtain a tax ID number, by filing Form W-7.
To file Form W-7, you either need to enclose original identification documents, which are then returned to you, or you need to file the form through a Certifying Acceptance Agent that has the authority to review your identification documents in a face-to-face meeting.
These forms are used by individuals. If you have a foreign business entity, e.g., a corporation, partnership, or trust, that is a completely different conversation, and it gets really complicated really fast. These forms cannot be used by a business entity.
Also: the term tax return refers to the form that you file with the Internal Revenue Service, and that is what the form is called, regardless of whether you get a refund. A refund is not a return, and a return is not a refund. Even if you owe tax to the US government, the form that you file is still called a tax return. This is a common misunderstanding even among US citizens.