Does one of you live in a community property state? Filing married filing separately gets tricky when even one of you is in a community property state. What states are involved---and who lives where? And....why do you want to file MFS instead of joint?
Community property states: AZ, CA, ID, LA, NV, NM, TX, WA, WI
It depends. If you live in a community property state and file Married Separate, for federal tax purposes, you must have all or most of spouse's income needed to complete the community property worksheet. Otherwise, you may not be able to e-file the return.