After-tax contributions

Payroll company, which by definition is in the business of processing payroll, asked my client to confirm tax retporting for after-tax contibutions.  To which I responded, "can you please have your payroll confirm who the HCE's are for 2021"? (kidding of course).

My understanding is that as far tax reporting goes on W-2s and 941s, these deductions are no different than 401k loan payment.  Am I correct?  i think its one of those things where I can't find any articles on how to reprot it on w-2's and 941s because there is simply no requirement to do so...  I'm trying to prove a negative is the other way to look at it.

Any help appreciated!

I did find this in the w-2 instructions:

Reported in box 14, but not in box 12.

• After-tax contributions that are not designated Roth contributions, such as voluntary contributions to a pension plan that are deducted from an employee's pay.

And Box 14 is apparently just a "whatever you want it to be" box, nothing regulatory about it.