For many Americans, it's the first order of business when they visit the HR department at a new job: enrolling in the 401(k) plan.
The tax-deferred savings plans have been promoted as one of the best ways to prepare for retirement, as traditional pensions become a thing of the past.
But the tax-free part is coming under greater scrutiny, as Congress looks under every couch cushion for the dollars needed to strike a deal on the looming fiscal cliff, and possibly re-write the tax code next year.
It's been a frequent target of would-be budget reformers across the political spectrum, including the Simpson-Bowles Commission and the Center for American Progress. Even President Barack Obama has eyed changes to the rules governing 401(k)s.