Thanks @dmertz . So I amend now and pay the additional income on that excess -- even though I can't withdraw it, it seems -- and then I pay taxes on it again when I am allowed to withdraw it. That makes sense. Thanks.
"the excess contribution does not add to your after-tax basis in the plan"
Why not? I guess the part that is still catching me up is that the investment basis of that additional contribution could end up outpacing the penalty over the course of the investment, I think? So couldn't I end up "cheating" the system by being allowed to have invested more up front due to excess contributions and letting it sit there for 15 years? Especially if I wait until retirement age to withdraw? Or am I not thinking about it correctly?
