A Roth Solo 401k is a version of the Solo 401k that lets you make after-tax contributions. That means you pay taxes on the money before you put it into the account, but your money can grow tax-free—and if you follow the rules, you won’t owe any taxes when you withdraw it in retirement. This can be especially helpful if you expect to be in a higher tax bracket later on. Like a traditional Solo 401k, it’s designed for self-employed individuals or business owners with no full-time employees other than a spouse. You can usually choose to split your contributions between Roth (after-tax) and traditional (pre-tax) if your plan allows it.