Common forms used by U.S. Citizenship and Immigration Services include forms G-28, I-131, N-400 and I-864, according to USCIS. These forms utilize 2-D barcode technology to help make processing more efficient.
Form G-28 is the notice of "entry of appearance as attorney" in matters outside the geographical confines of the United States, notes USCIS. Form I-131, which may require a fee, is the application for a travel document. Form N-400, the application for naturalization, requires a $595 fee for those 75 or older and a fee of $680 for everyone else, as of 2015. Form I-864 is the affidavit of support. All USCIS forms are available for free download at the USCIS website. The USCIS cautions that no one should pay for any of its forms.