What do I do if my ex-husband claim our daughter for about 5 years straight but in our divorce decree, it says to alternate years?

IRS regulations provide that the custodial parent has the right to take the exemption for the child. The custodial parent is the one where the child sleeps the most nights during the tax year.If the child sleeps at each parent's home equally then it's the parent with the higher income. So if you're the custodial parent, go ahead and take the exemption. The IRS will cross reference and send you both a notice, then you give the IRS a copy of your divorce decree which states you have more nights (or you have equal nights and you're the higher income spouse). You win. If you're the noncustodial spouse, your ex needs to sign and give you IRS form 8332 for they years you can take the exemption. If he doesn't give you the form, have your divorce attorney file a contempt of court action against him.