generally married filing joint is going to produce the lowest combined tax liability and the biggest refund or the smallest balance due. married filing separate results in loss of certain credits and if one itemizes the other must also or if one takes the standard deduction both must take it. about the only time married filing separate is better is when both can itemize and one with the lowest income has the highest medical expense.
you may want to buy the desktop software to check various scenarios. Married joint and married filing separate.
or you can do this online. do your separate return see the tax summary page. delete it. do your spouse's separate return see the summary page then delete it. then do joint. if your spouse didn't have any income don't bother with the various scenarios, joint will be best.
