My taxes were rejected with an SEIC-F1040-506-02 code - I can't claim my dependant because they're already claimed. However, he is listed as a non-dependant qualifying for dependant care payments only

[macuser_22]

If you are the custodial parent where the child physically lived more then half the year then only you can claim the EIC.   It sounds like the non-custodial improperly claim the EIC and should amend to remove it.

Your only option is to properly claim what you are entitled to and print and mail your tax return.   You will be unable to e-file this year.   Even it the other parent amends, the  will not allow an e-file this year.

[Opus 17]

Assuming that you are the custodial parent, this situation would be caused if the noncustodial parent filed an incorrect tax return. The noncustodial parent is supposed to indicate that the child did not live with them, and they can only claim as a dependent if they send the IRS a signed form 8332 dependent release, that you have provided. If they do this correctly, their tax program will claim the child tax credit but nothing else and it will not create a conflict with your tax return.  It sounds like the other parent may have indicated that the child lived with them all year so that they do not need to file a form 8332 and allowing them to claim EIC and other tax benefits incorrectly.

You simply need to print your return and mail it in and let the IRS sort things out. You should expect the IRS will send letters to both parents and you will need to provide proof that the child lives with you more than half the nights of the year.