20 CFR § 416.1603 - How to prove you are a resident of the United States.
(a) What you should give us. Your home address in the United States may be sufficient to establish that you are a resident. However, if we have any reason to question that you are a resident of the United States we will ask for evidence. You can prove you are a resident of the United States by giving us papers or documents showing that you live in the United States such as -
(1) Property, income, or other tax forms or receipts;
(2) Utility bills, leases or rent payment records;
(3) Documents that show you participate in a social services program in the United States; or
(4) Other records or documents that show you live in the United States.
(b) What “resident of the United States” means. We use the term resident of the United States to mean a person who has established an actual dwelling place within the geographical limits of the United States with the intent to continue to live in the United States.
(c) What “United States” means. We use the term United States in this section to mean the 50 States, the District of Columbia, and the Northern Mariana Islands.