If you are planning on filing as Married Filing Joint, and she does not
have and does not currently qualify for a Social Security Number, then
he will need to apply for an ITIN. The following answer that I gave on
this subject should be of assistance in helping you to file your return:
To obtain an ITIN, you must complete IRS Form W-7, IRS Application for Individual Taxpayer Identification Number.
The Form W-7 requires documentation substantiating foreign/alien status and true identity for each individual. You may either mail the documentation, along with the Form W-7, to the address shown in the Form W-7 Instructions, present it at IRS walk-in offices, or process your application through an Acceptance Agent authorized by the IRS.
The IRS provides the following instructions on how to an apply for an ITIN:
do I apply for an ITIN?
Use the latest revision of Form W-7, Application for IRS Individual Taxpayer Identification Number to apply. Attach a valid federal income tax return, unless you qualify for an exception, and include your original proof of identity or copies certified by issuing agency and foreign status documents.
Because you are filing your tax return as an attachment to your ITIN application, you should not mail your return to the address listed in the Form 1040, 1040A or 1040EZ instructions. Instead, send your return, Form W-7 and proof of identity and foreign status documents to:
Internal Revenue Service
Austin Service Center
P.O. Box 149342
Austin, TX 78714-9342
You may also apply using the services of an IRS-authorized Acceptance Agent or visit some key IRS Taxpayer Assistance Center in lieu of mailing your information to the IRS in Austin. Taxpayer Assistance Centers (TACs) in the United States provide in-person help with ITIN applications on an appointment basis only. The IRS's ITIN Unit in Austin issues all numbers through the mail.
For additional information about ITINs, please see the following IRS topic: