Is it ok to file taxes separately when married when the spouse is a foreigner who just got a temporary green card?

According to the IRS, there are 2 tests that determine if a foreign citizen is considered a resident alien for US tax purposes, the green card test or the substantial presence test

The green card test - You are considered to have met the green card test if at any time during the calendar year you were a lawful permanent resident of the United States according to the immigration laws, and this status has not been revoked or administratively or judicially determined to have been abandoned.

So if your spouse has a green card, if is more than likely that your spouse meets this green card test which would mean that your spouse will be treated as a resident alien.

Resident aliens must follow the same tax laws as U.S. citizens. If you are a resident alien, you must report your worldwide income from all sources, that is, income from both within and outside the United States. You will file a Form 1040EZ (PDF), Form 1040A (PDF), or Form 1040 (PDF) depending on your tax situation. See this link for general filing requirements for married filing separately for a US citizens or resident aliens :

https://turbotax.intuit.com/tax-tools/tax-tips/IRS-Tax-Return/Does-Everyone-Need-to-File-an-Income-T...

Please note that if you are as married filing separately, when TurboTax prompts you for your foreign spouse's SSN, you will leave it blank. (TurboTax allows only a numeric entry in the SSN field). You must hand-write "NRA" in all of the places on your tax return that require your foreign spouse's SSN before mailing in your return (you will not be able to efile your tax return so choose "file by mail" in TurboTax).

However, if you file as married filing separately, you can claim an exemption for your spouse if your spouse had no gross income, isn't filing a US tax return, and wasn't the dependent of another person. But, if you do take an exemption, you will need an (ITIN) for your NRA spouse.

In TurboTax, if your foreign spouse does not have a social security number (nor any prior Individual Taxpayer Identification Number):

• file as married filing separately
• leave spouse's Social Security Number blank  (when prompted to enter information into TurboTax)
• when you are getting ready to file your return in TurboTax, skip past the error message section in TurboTax regarding the missing SSN (but make sure that this is the only error message that you are getting
• under "file" tab, select that you want to "file by mail"
• print a paper copy of your tax return to mail to IRS.

These additional requirements are necessary if filing married filing jointly or married filing separately and you are taking an exemption for your spouse:

• apply for an Individual Taxpayer Identification Number (ITIN) using Form W-7 (Click ITIN)
• attach a copy of your Form W-7 (along with the necessary supporting documents) to your tax return (For the supporting documents, one option is for your spouse to get a certified copy of his/her passport which will need to be included with your tax return filing. Have your NRA spouse check with his/her local embassy regarding this certified copy) Click here for IRS website ITIN - Frequently Asked Questions
• mail your tax return along with your attached W-7 and supporting documents to the IRS. According to the IRS, 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
       ITIN Operation
       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