You can call the IRS however you have to send a letter of explanation and your taxes by postal mail. Do this as soon as possible as it can take up to a year for corrections to be processed. The other option is you have to claim your taxes always before the other parent by sending them by the first due date AND/OR submit a modification to the parenting plan to the court asking that you claim the taxes and that their is no other person providing half of the support in addition to the other facts of your case.
A parent or custodian claiming has to have the child in their custody at least 180 days a year varying from state to state. Look up the rules in your state for claiming taxes on a dependent and make sure you add this to your tax letter or court documentation. In addition, if you have or can not not file taxes you can file for the non-tax stimulus through a link on the federal IRS. gov site.
Other: You can ask the court for the money taken to be paid back to you if the IRS does not take the money. In some circumstances both parents actually claimed and received the full stimulus amounts. If the other parent who does not have custody or visitations is having financial difficulties they can submit a motion to the Child Support Subsidy Department for "Forgiveness" of past debt.
