Depending on the state from which you are filing, the Department of Treasury, Internal Revenue Service has four regional offices where you will be able to mail your federal tax return. The offices are located in the Kansas City, MO for the east coast, Atlanta, GA for the south, Austin, TX for the central areas and Fresno, CA for the pacific and mountain areas, with Alaska and Hawaii also using the CA office. For international filing, use the Austin, TX office, however non-permanent residents of Guam and US Virgin Islands will use their respective offices in their country. Also, the full address information will be provided on the forms you will be using to complete your federal tax return. Information is available on the IRS secure website, irs.gov, as well.