@ConfusedByTaxes1983
Well you are confused because you are mixing up 2 different things ... the third stimulus advance payment and the advance CTC payments.
As already mentioned ... if you did not get the full third stimulus payments due to income limitations and you now qualify using the 2021 income then you will get the rest of the stimulus on the 2021 return.
Now for the CTC advance ... like the stimulus payment if you did not get everything you should have in advance then you will get it on the 2021 return.
Just complete the interview process in the program and when asked how much you got of each advance simply enter what you did already receive ... do NOT add them together ... they must be entered separately and in their own sections.
