Using only my 2020 1040 tax return forms where do i find the amount that I enter that comes from the IRS letter 6419 that I do not have.

[DoninGA]

As previously stated you can only enter the advance child tax credits you received from the IRS during the timeframe of July thru December 2021 on the 2021 tax return.  Not 2020.

To enter, edit or delete the advance child tax credit

• Click on Federal Taxes
• Click on Deductions & Credits
• Click on I'll choose what I work on (if shown)
• Under You and Your Family
• On Child and Other Dependent Tax Credit, click on the start or update button

Or enter child tax credit in the Search box located in the upper right of the program screen. Click on Jump to child tax credit

[VolvoGirl]

It is NOT on your 2020 return.  If you don't have the letter 6419 you need to check your bank account to see how much Advance they sent you in 2021 (July-Dec).  And please stick with your first question.  You should not be starting new posts.  Add on to the existing one.

The new Child Tax Credit for 2021 raises the cut off age from 17 to 18 and makes the credit $3,000 (3,600 for a child under age 6).  Check 1040 line 28 for it.  You might have got the Advance Child Tax Credit for Half during the year.  You need to enter what you already got so you don't try to claim it again.  

Line 30 and 28 is only if you didn't get the full amount or qualify for more. 

You should also get letters 6475 and 6419 showing what the IRS sent you.  Turbo Tax blog on IRS Letters 6419 and 6475

IRS Letters 6419 and 6475 for the Advance Child Tax Credit and Third Stimulus: What You Need to Know...