Why did my return get smaller when I put in my 3rd stimulus check amount? Not the child payments thing just the stimulus check

[xmasbaby0]

What you may not realize is that as soon as you began to prepare your tax return, the software was giving you the $1400 and it was shown on that "refund monitor" -----but when you entered that you received it already, the software had to reconcile the payment you received,   You cannot get it twice---so it looked to you like you "lost" $1400.   You did not lose it---you just cannot receive it twice.

[VolvoGirl]

Did you already get the full amount?

  Your 2021 return starts out by assuming you didn't get any Stimulus payments so it gives you credit for the full amount and your refund was too high.  Then near the end you enter how much you actually got so it only gives you the difference if any.  So you don't get it again.

Look at your tax return.   It is not added as income anywhere or subtracted anywhere.  The Recovery rebate credit on line 30 is only if you didn't get the Stimulus payment or qualify for more.