An innocent spouse claim is when you are being held responsible for a debt caused by a joint tax return with your former spouse. An innocent spouse claim can only be filed after a divorce.
The problem is, when you file a joint return with your spouse, you are signing your name that all the facts are correct and you are both legally and equally responsible for the return. It's called "joint and several liability." If there is a tax debt, and you have more money than your ex, the IRS can collect 100% of the debt from you no questions asked.
Filing the innocent spouse forms means you are asking the IRS to not hold you responsible for your spouse's actions. You generally have to argue that your spouse deceived you or concealed information from you, and therefore you are not responsible even though you signed a joint return. Or, you can ask for "equitable relief", which means you are asking the IRS to only hold you responsible for part of the debt for reasons of equity or fairness.
The bottom line is there is no guarantee the IRS will honor the claim at all. It depends on the particular facts and circumstances. If they don't accept your argument you could still be on the hook for 100% of the debt. You will just have to wait and see what they say. You may have the right to appeal, and if the amount is significant you may want legal representation.
