was question 29C checked yes on your 1120C. if so, you are telling the IRS you are exempt from filing form 4626. it may be that the IRS computers are not programmed properly so these notices are sent out in error.
Form 4626 is required to file with a corporation tax return unless a filing exclusion applies. Based on IRS Form 4626 instruction, taxpapers can choose to apply the safe harbor method (simplified method) if qualifies. IRS clarifies rules for new corporate alternative minimum tax generally applies to large corporations with average annual financial statement income exceeding $1 billion.
If taxpayer qualified for safe harbor method (most corporation may qualify), they can click the "yes" box on Form 1120 Sch K Line 29c to avoid filing Form 4626.
if you are exempt you can respond to the notice by saying you used the safe harbor simplified method and therefore are exempt from filing or you can submit form 4626
