File your tax return and if your husband files children as the dependent, your return will be rejected. You would then need to file a return on paper. Later you'll receive a letter from the IRS, stating that your child was claimed on another return. It will tell you that if you made a mistake to file an amended return, and if you didn't make a mistake, do nothing. The other party will get the same letter you did. If one of you doesn't file an amended return, unclaiming the child, the next letter, from the IRS, will require you to provide proof. Be sure to reply in a timely manner.
