Ok ... I got your answer ... you filed married with one child on the 2020 return correct ? That would account for the $4200 third stimulus check you got ( the second one that came in Jan does not get reconciled on the 2021 return). So you needed to enter 4200 once ( or 2100 you and 2100 spouse) when asked how much you got in advance. If you only answered 2100 and you are filing a joint 2021 return with no dependents then the program thought you were short $700 since you should have gotten 2800. This was a data entry error on your side and the IRS caught the error and corrected it automatically. You probably only got one IRS letter 6475 reporting 1/2 of the stimulus payment so you misread the screen instructions which is a common error this year and last while trying to reconcile this blasted stimulus payments.
