Do "After Tax" non ROTH 401(k) contributions go into box 12b (W-2), in box 14 or not at all? If they go into box 12b, how is it coded 2 avoid counting against the 24500?

[mhudick]

My wife's W-2 lists her "After Tax" non ROTH 401(k) contributions in box 12b and codes them "AA", which is the code for elective contributions to a ROTH 401(k).

Her 401(k) did not have a ROTH option. So there is no way that this W-2 is correct. 

Compounding that is Turbo Tax which takes that information and adds it to her 401(k) elective deferrals of $24,500. That produces an excess contribution of about $12,000, which is also wrong..

The IRS instruction set for the W-2 does not discuss "After Tax" contributions to a non ROTH 401(k) so I am of the opinion that it does not belong on the W-2, unless it can go into box 14 for information purposesonly.

The literature supports the IRS position that "After Tax" non ROTH contributions are placed into a taxable 401(k) component and counts against the maximum annual 401(k)contribution, but not to the taxable.

So how do I fix this?

[dmertz · Accepted solution]

If the contributions were after-tax contributions to the traditional 401(k) (normally tracked in a separate sub-account, but not a designated Roth account) your wife must obtain a corrected Form W-2 from her employer. 

Code AA is only for Roth 401(k) contributions.  After-tax traditional 401(k) contributions are not reportableon a W-2, although the employer can note them in box 14 for informational purposes.