Has someone forged your name on a Tax Return? Maybe your spouse?  What do you do?
When a spouse establishes his or her signature on a joint return was forged and there was no tacit consent to the return as filed, the joint election will be  invalid.
Again, the relief from joint and several liability provisions do not apply. Why? Because the IRS will not accept the tax return once they become aware of the proved forgery.

The individual claiming his or her signature was forged is not jointly or severally liable for liabilities arising from such a return if the signature was indeed forged. The Cincinnati Service is designed to work these cases.  The  IRS form Form 8857, Request for Innocent Spouse Relief will be used in these cases.
If you look at line 11 of the Form 8857, Innocent Spouse Relief, it asks the Requesting Spouse whether the signature was forged.
A married filing separate tax return may need to be secured from the spouse claiming forgery if a return is required for the period, or if the taxpayer may have been entitled to a refund. You will have to document the case for the IRS. You will want to get copies of your signature and develop a case file for the IRS. It makes cases easier to work.

A Requesting Spouse who raises the issue of forgery and later determines he or she would owe more tax if he or she filed separately, may choose not to pursue the issue of forgery.Yes, you may not want to pursue the case. It will be cheaper to leave it alone.
In situations where the spouse claiming forgery failed to file despite having a filing requirement, the circumstances surrounding the alleged forgery should be investigated. An interview with the other spouse can be considered by the Internal Revenue Service when developing the tacit consent issue. The IRS as a practical matter has very little time to work these cases. However, on a larger dollar case it could fly.
The Internal Revenue Service can consider referring the individual who forged the signature and any other individual associated with the forgery to the Criminal Investigation Division.
Side note:  Cases that can go to the CID would be large dollar multiple year type of cases or possible high profile individuals.