SEP Simple not allowing to file. Box 12 code S

A TurboTax employee posted this:

. On January 8, 2024 (i.e., just two weeks ago) the IRS released a notice describing many changes required to implement the Secure Act 2.0 - I believe that this is what "We're updating how SEP and simple plan contributions are reported on the tax return based on new guidance from the IRS." is referring to.

Indeed, Section 601 of the Secure Act 2.0 refers specifically to Simple and SEP Roth IRAs. Code S in box 12 refers to how to handle a SIMPLE plan.

These last minute IRS (and law) changes inescapably cause delays on the part of TurboTax and other tax processors. 

It will take time for TurboTax to understand all the ramifications of this IRS Notice and then code and test the changes. The IRS is not open for filing until January 29th so you have some time to wait.