You don't need his permission. He needs your permission to claim the kids. The custodial parent has first priority on
claiming the children on her taxes; regardless of the amount of support
provided by the non-custodial parent. The non-custodial parent can only claim
the child as a dependent if the custodial parent gives permission (on form
8332) or if it's spelled out in a pre 2009 divorce decree. (without conditions - usually the payment of child support). The IRS goes by physical custody, not legal custody (you said "the kids are with me more.").
If someone else claimed your
child inappropriately, and if they file first, your return will be rejected if
e-filed. You would then need to file a return on paper, claiming the
child as appropriate. The IRS will process your return and send you
your refund, in the normal time. Shortly (up to a year)
thereafter, 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 to 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.
Winner gets the tax benefits;
loser gets to pay the IRS back with penalties and interest. The
custodial parent almost always wins. The non-custodial parent can only
claim the child as a dependent if the custodial parent gives permission (on
form 8332) or if it's spelled out in a pre 2009 divorce decree.
https://www.thebalance.com/claiming-same-dependent-audit-risk-3193030
_____________________________________________________________________________________________________________
There is a way to split the tax benefits. For future negotiations with the
other parent (and maybe even for this year) the following info may be of use: :
There is a
special rule in the case of divorced & separated (including never married) parents.
When the non-custodial parent is claiming the child as a
dependent/exemption/child tax credit; the custodial parent is still allowed to
claim the same child for Earned Income Credit, Head of Household filing status,
and day care credit. This "splitting of the child" is not available
to parents who lived together at any time during the last 6 months of the year;
then only one of you can claim the child for any tax reasons. The tax benefits
may not be split in any other manner.
Note in particular
that the non-custodial parent can never claim the Earned Income Credit, Head of
Household filing status or the day care credit, based on that child,
even when the custodial parent has released the exemption to him.
