I'm 33 and I just realized I've been contributing to the wrong 401k option for 5 years. Here's how I found out and what I'm doing about it.

My company offers both a traditional 401k and a Roth 401k. I had selected the Roth 401k at my original enrollment because I'd read that Roth was generally better and didn't think harder than that. At the time I was earning $45k and in the 12% bracket — Roth was correct.

Since then my income has grown to $115k, putting me in the 22% bracket. For the past 3 years I should have been contributing to the traditional 401k to get the deduction at 22% and pay tax in retirement at what I expect will be a lower rate.

Fix: I've switched my future contributions to traditional. The past contributions are already in the Roth 401k and that's fine — it's not wrong to have Roth money, especially at age 33 where it has decades to grow. I've updated my allocation going forward.

The lesson: the Roth vs traditional decision isn't permanent and it isn't binary. Review it any time your income changes significantly.