Proof of residency: A deed, lease agreement, or resident manager's letter is acceptable. Supporting documentation may be required.Property tax bill or statement. Records from a financial institution. Documents Needed for Registration. Proof of Residency in Fairfax County. To establish a domicile in Virginia, you must show you have legal residence in the state with the intent to remain indefinitely. Rental agreements are binding contracts and often have provisions requiring tenants to pay fees for not completing the lease term. Residents file Form 760.