Claiming A Dependent

I'm preparing a return for an adult son of a valued client. The son works and lived with his girlfriend for the entire 2019 year. They have three young kids together who also live with them. I won't be preparing the girlfriend's return, just the son's. Let me preface this post by saying this is not the type of work I do and am only preparing this return at the request of a very good client.

I believe that all three children are a qualifying child of both the boyfriend and girlfriend. I get the sense that in the past they've claimed the children based on whose return will produce the best tax results. Horse trading, for lack of a better phrase.

The son claimed one child as a dependent in 2018 and wants to claim 2 children this year. As long as the children are the QC of both the boyfriend and girlfriend, am I wrong in concluding they can agree each year how to split the kids as far as who claims what child.

Am I missing something?

If a child meets the qualifying child requirement for each of them them, one or the other may use that child as a QC but not both. Since they both qualify, either may use the child as a QC. If they can't agree, IRS will decide for them using the tie-breaker rules. IRC 152(c)(4).

The taxpayer claiming the QC gets the tax benefits including child tax credit, HoH filing status, dependent care credit, earned income credit. They cannot pick and choose which person gets the benefits. The benefits go with the QC.

Since you aren't preparing the girlfriend's return I would get it in writing that it is your client's responsibility to make sure his gf didn't claim the child because if the efile rejects and you have to revise it, there will be an extra charge.