If you are legally married, you must file as married, either married filing jointly or married filing separately. Filing jointly has the lowest tax rate and better treatment of deductions and credits. Since your spouse is eligible for an SSN, you should wait to file until the SSN arrives and you can use it on the return; certain tax benefits are not available if your spouse does not have an SSN. Don't file early using some other status and plan to amend later when the SSN arrives.
