[SaberTail]

I can think of one common situation for typical HN readers. If you make too much money to contribute to a Roth IRA, and your workplace offers a 401k (which means traditional IRA contributions will not be deductible), then you can still put money into a Roth IRA by contributing after-tax dollars to a traditional IRA and doing a backdoor Roth conversion[1].

The problem is that when you do one, you pay taxes pro rata on any pre-tax funds in your IRA. If your 401k is pre-tax dollars (most are), then if you convert a 401k to an IRA, you will start having to pay taxes every time you try to do a backdoor Roth.

[1]http://www.rothira.com/what-is-a-backdoor-roth-ira