Anyone who resides in the United States can apply for this certificate. A domicile document is critical for your I-864 Affidavit of Support.Log in to the NSP Application Form. 15. Navigate to My Profile in the menu. 16. I understand you're seeking guidance on obtaining a Domicile certificate in the US. May I ask, which state are you currently residing in? Take your birth certificate and a bill or your rent or mortgage papers with your name and home address on them.