Going through the back door can pay off for high-income retirement savers.

We’re talking about the backdoor route into popular Roth individual retirement accounts, which offer tax-free income in later life.

The front door into Roths is shut for many investors. Married couples earning $191,000 or more and singles earning $129,000 or more in 2014 are barred from contributing directly to Roth IRAs.

But there’s a simple detour that works for many of them. They can put money into a traditional IRA—and then roll that into a Roth IRA, getting all the benefits.