"Married couples filing separately are only eligible for $1800 and $1500, respectfully."  That is not how the software treats it. I know a married couple that filed married seperate in 2020. The mother took 2 dependent children. The father took 0 dependents. The mother received $3000 in Advanced Child Credit in 2021 and $4200 in EIP payments. The father received $0 in Advanced Child Credit and $1400 in EIP payments. In 2021.  The IRS has stated that AdvCTC Letter 6419 MUST match what is reported by the tax payer. The mother received IRS letter 6419 with $3000 and 2 eligible dependents and a EIP letter showing $4200. The father received no AdvCTC letter 6419 because he had $0 Advanced Child Credit and a EIP letter reporting $1400. For the 2021 tax year the father is going to take the 2 dependent children. When he puts $0 amount in for Advanced Child Credit the software gives him a credit of $3000 and when he puts in $1400 reported for the EIP it gives him an EIP credit of $2800. For the 2021 tax year the mother is claiming 0 dependents. When she puts in $3000 for Advanced Child Credit from her AdvCTC letter 6419 the IRS  is only "clawing back" $1100 of the $3000 Advanced payment based on her wages. And she does not have to pay any EIP payments back. No where does it ask when your filing married seperate if your spouse received any Advanced Child Credit or EIP payments. No where in the IRS instructions does it say Married filing seperate couples are to add their payments together. It does say if Married filing joint to add their payments together.