Perhaps two of the sweetest words retirees long to hear are "tax free."

Though workers are told to put every spare pre-tax cent into a traditional 401(k) at work, the reality is that once the time comes to tap that account for income in retirement, income taxes will follow.

Here's the bright side: You can create a pool of tax-free retirement income. If you're lucky enough, you can even do it at work.

Say hello to the Roth 401(k): You pay taxes upfront on your savings, have them accumulate tax-free and then take withdrawals free of taxes in retirement, as long as you meet certain conditions.

This year, you might even spot one of these plans at work. Nearly 85 percent of the 106 employers polled by Callan said they offered Roth 401(k) accounts in 2018.

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