how did you answer question 29c on the 1120
if "no" then 4626 is required if "yes" not required
however, it may be that the 4626 instructions conflict the the 1120 questions
4626 part 1 line 8/9 seem to require it
so this may be a situation where the IRS doesn't understand its own rules and is issuing the notices improperly.
Based on IRS Form 4626 instructions, taxpayers can choose to apply the safe harbor method (simplified method) if qualified. IRS clarifies the rules for the new corporate alternative minimum tax generally applies to large corporations with average annual financial statement income exceeding $1 billion. (Under $1B and safe harbor elected no filing required)
If the corporation qualifies for the safe harbor method (most corporations using Turbotax business probably qualify), they can click the "yes" box on Form 1120 Sch K Line 29c to avoid filing Form 4626.
if you checked yes to 29c and qualify, which is likely, then the IRS should never have issued the notice. I admit I'm guessing but I think very few Turbotax 1120 filers would need to file.
irs 4626 webpage - see the special rules section
https://www.irs.gov/instructions/i4626#en_US_2023_publink1000124757
If you have received an IRS letter regarding this issue, you may 1) file an amended 1120 with line 29c box checked yes. if you qualify or, 2) you may also respond to IRS letter with Form 4626 o, 3) respond with a signed and dated note that you qualify for the safe harbor and had checked question 29c yes, and therefore are exempt from filing.
