Can I amend/ adjust line item 30 on 2020 tax return to reflect 0.00? Thank you !

Why do you need to indicate 0 for the recovery rebate credit on Line 30 of the 2020 tax return?

Did you receive a notice from the IRS that you were not eligible so the credit was not issued to you from the original 2020 tax return?  If so, there is no need to amend the 2020 return.

Why?   Line 30 on a 2020 return is the line for the recovery rebate credit.   You would have used that credit if you did NOT receive the first or second stimulus check.   The IRS checked every return that had an amount on line 30.   If you already received the stimulus check(s) and had an amount on line 30, the IRS changed your refund for you and disallowed the credit.  Is that what happened?   Why do you want to amend and change it?