My ex husband brought me a form to sign during a stressful time wanting to claim our daughter every other year on his taxes, not realizing what it was I signed it.Now I found out it was a 8223 tax form. We don't have any court order saying he can claim her I have full custody of my daughter and he only has visitation every other weekend. What can I do now?

Ignore him, if there is no court order signed by the judge and he is not providing over 1/2 of the support of the child, you can not give away your rights to claim the child. Merely send him a letter resending your permisison to claim child.

Thanks so much I was very worried

The custodial parent is the one who claims the child as a dependent unless there is a court order stating otherwise or unless the custodial patrent has signed form 8332. It doesn't matter whether the father provides more than half the chold's support or not.

You don't say whether you signed form 8332 for an earlier tax year or for tax year 2010 - please clarify that. If you signed it for 2010, you are out of luck - he will attach it to his return and the IRS will recognize it as valid.