In Turbo Tax I only see the option for Roth 401(k) and not traditional after tax. Are these the same in Turbo Tax ?

[neeson]

In my emp. 401K account, I spillover contributions to after tax contributions after I cross the IRS limit.

[dmertz]

After-tax contributions to your traditional 401(k) account are not reportable on your tax return, except in the case where you qualify for a Retirement Savings Contributions Credit.

[neeson]

To clarify, I have got a 1099-R and these are after tax contributions towards the mega backdoor roth.  I assume I need to report the details presented in the 1099-R. Turbo tax doesn't give me the option to specify mega backdoor roth when providing the details for this 1099-R. Turbotax only asks if I "moved this money from a 401(k) to a Roth 401(k)?".

Also, found this https://thefinancebuff.com/mega-backdoor-roth-in-turbotax.html. (Assuming this is up to date and accurate) to be useful.

[dmertz]

As I said, your after-tax contribution to the traditional 401(k) is not reportable on your tax return.  What is reportable (the reason for the Form 1099-R) is the subsequent In-plan Roth Rollover of those funds, so answer Yes when TurboTax asks if you moved this money from a 401(k) to a Roth 401(k).  That's exactly what you do to accomplish the Mega-backdoor Roth.