1st stimulus

You will amend your return- see How to amend .

To enter the information for the stimulus payment, 

Enter all of your federal return information as you would normally. During the Federal Review, we’ll check if you meet eligibility requirements for the stimulus payment. If you meet the requirements, you'll see a Did you get a first or second stimulus? screen. We'll ask a few questions about any payments you've already received and then let you know if the Recovery Rebate Credit applies.

• If you need to make any changes to your stimulus credit responses, search for stimulus and select the jump-to link at the top of the search results to return back to the section. Enter your updated info and Continue.

Why would you need to amend the return? did you enter the incorrect amount of the first two stimulus payments you received? 

If you are eligible for any additional stimulus (and you may not be) it would have been posted on Line 30 of your tax return.  What is on that line? 

it is possible that you are not eligible for more Recovery Credit.

ps the 3rd stimulus is part of next year's tax return reconciliation.

@MaryK4 - why suggest a amendment?  Line 30 reconciles everything, unless the amount received for the 1st two stimulus payments is incorrect to begin with and I suspect the IRS would catch that in any event before issuing the refund.