If one spouse has entered into an agreement (known as an offer in compromise) to pay the IRS less than what is actually due, plus interest and penalties, it is still possible for the IRS to go after the other spouse to collect the outstanding monies. In addition, an indemnity clause in a marital agreement (where one spouse agrees to hold the other harmless for any tax liability) offers NO real protection from the IRS. In fact, the IRS can even seize a joint taxpayer's assets or property even AFTER it has been divided in a divorce decree to satisfy an outstanding account. If you marriage is annulled, the IRS views this as if the marriage had never actually taken place. Therefore, if joint returns were filed, then corrected, separate returns will have to be re-filed.
Once the decision to file a joint return is made, it should also be collectively determined what to do with any refunds or additional taxes that may occur. This decision should also be documented in writing as well to avoid any future misunderstandings or hostility. A simple solution would be to agree to split any refund or share an equal burden of any additional tax that may come due.
The tax issue is perhaps the greatest example of how important it is to have all arrangements with respect to the impending divorce documented in writing. Oftentimes during a divorce, the spouses reach understandings with respect to alimony and child support, but never bother to get the results down in writing on paper. Alimony is actually tax deductible, however, it will need to be documented by either a written agreement signed by both parties or by an actual court order. In other words, in the eyes of the IRS, word of mouth agreements are not enough to warrant a deduction. If you are receiving alimony, that too is income that must be reported. However, in order for alimony payments/receipts to be deductible, separate returns must be filed. Child support is never deductible, either for the parent who pays it, or the parent who receives it.