The AGI is a calculated number so it cannot, by itself, be changed unless you change the numbers that is used in the calculation.  What is it that you need to change?

I received a 1099B after my return and refund.  Proceeds: $575.50 and cost basis $500.00.  I downloaded it from the Broker.  Do not recall making other changes.  

Can I reverse the amendment and start the ammendment over?

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@hborkfamily wrote:

I received a 1099B after my return and refund.  Proceeds: $575.50 and cost basis $500.00.  I downloaded it from the Broker.  Do not recall making other changes.  

 

Can I reverse the amendment and start the ammendment over?

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See this TurboTax support FAQ for canceling or undoing an amended return when using the desktop CD/Download editions - https://ttlc.intuit.com/community/amending/help/how-do-i-cancel-or-undo-an-amended-return-in-the-tur...

The gain of $76 (rounded up from $75.50) adds $76 to your AGI.

The AGI does match last years AGI and I keep getting rejected

ENTER 0 FOR AGI. The IRS took a long time last year to process 2020 returns so the AGI didn't get entered in time.  Especially if you mailed it.  That works for most people. See,
https://ttlc.intuit.com/community/rejections/help/what-if-i-entered-the-correct-agi-and-i-m-still-ge...

How to correct the AGI in the Online version
https://ttlc.intuit.com/community/agi/help/where-do-i-correct-my-agi-in-turbotax-online/00/26311

If you can’t get it to efile you will have to print and mail it.
https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...

Be sure to attach copies of your W2s and any 1099s that have withholding on them.  You have to mail federal and state in separate envelopes because they go to different places.  Get a tracking number from the post office when you mail them for proof of filing.

You need to enter the AGI off the originally filed return which you can find on the amended return form 1040x line 1 column A.