Any sugestions about form 4626?

You would only need to file Form 4626 if your company's average annual financial statement income exceeded $1 billion.  It's possible a box was checked accidentally when you completed the business return.

I recommend referring to the instructions provided by Faith C here for guidance on how to proceed with the letter from the IRS.

There are several threads about the Form 4626 problem. I suggest new victims go here: https://ttlc.intuit.com/turbotax-support/en-us/help-search?advanced=false&allow_punctuation=false&filter=location&location=category%3Aen-us&q=4626&uid=m40hv86o

and search for “4626” then read the various threads. This is clearly a serious error in the 2023 version of Turbo Tax for Business. I will guess it is sufficiently serious that Turbo Tax will take the trouble to fix it for the 2024 version.