Can I change my Filing status from MFJ to MFS for 2008 period? I did not knew that my husbands company would be filing the returns. They have filed his returned for 2008 as MFS. What is the process to change?

Your question is a little confusing. You're asking if you can change to MFS, but you said your return was filed MFS. In which case they filed as you desired.

If your question is can I switch from MFJ to MFS, as the original return was filed MFJ for 2008, the answer is yes. You make swithch by filing a form 1040X, to make a correction on your federal return.

However, you can only switch to MFS after 4/15, if you can prove the original filing was invalid, i.e. your signature was forged. When you submit your F 1040X, you must attach documents to prove it was not your wish, done without your permission, you did not sign it etc.. Any documents you can get from third parties, or your spouse, signed, will help your position. It is your responsibility to prove this, if the IRS is not satisfied it can be disallowed.

If they disallow your request, you can appeal their findings. These procedures will be in the denial letter generally.