What is a Roth 401K? A Roth 401(k) is an employer-sponsored retirement savings account. Unlike a traditional 401(k), you don’t receive a tax break when you contribute to a Roth 401(k); you pay income tax on the money you contribute. Your contributions grow tax-free in the Roth 401(k). When you are 59 ½, you can withdraw the money from your account tax-free. With a traditional 401(k), you receive a tax break for your contributions, but the withdrawals you take after age 59 ½ are taxed at your ordinary income rate. The bottom line: If you prefer to pay taxes now and have tax-free income in retirement, choose a Roth 401(k). If you prefer to pay tax later and get a tax break now, choose a traditional 401(k).