"Technically" she is not paying a spouse or a relative. Yes, she pays taxes on her wage. Half of what she pays daycare is a credit back to her (only in 2021). He can't get a job elsewhere. So she pays him instead of daycare. He claims his income and the EIC covers his social security tax. Technically this is legal, even if it smells. This was never an issue before because rules in 2021 changed as regards Form 2441 and EIC. The MFJ status is unhelpful to clients at both the low and high income end. Over my 40 yrs as a tax preparer, I have advised several clients not to marry.