If you are filling separately and you have not discussed who’s claiming the kids..... you need to be the first to file, because if he files before you and claims them, you will get rejected and audited. Happened to me by accident one year because my idiot ex forgot which years he claimed on. It got fixed, but it was a pain.
We agreed to split the kids he even said I could take D14 since she gets the higher tax credit so either I take the older 2 or her. I MUST file first I just feel so guilty. Even if I let him have D14 he will owe A LOT more not only because of the higher tax bracket but because I'm the one who put aside money throughout the year to cover this.