1. Complete IRS Form W-7.
2. Complete your federal and state tax returns using the number 999-88-9999 in place of a Social Security Number.
3. Print the tax returns and cross off the 999-88-9999 from the SSN field. Do not attempt to e-file your return.
4. Write "Applying for ITIN; Application attached" next to the SSN field.
5. Mail the signed federal return, the completed Form W-7, and all documentation required by the Form W-7 Instructions to the address specified in the Form W-7 Instructions. (Alternatively, you may choose to take all this information in-person to a local IRS office for processing.)
6. If you need to file a state tax return: Mail the signed state return and a copy of Form W-7 to your state's regular filing address.
The free e-file from TurboTax is easy to use with a nice design.