If you want to save for retirement, an employer-sponsored 401(k) plan is a good place to start. Consistently putting money into one could even make you a millionaire: The number of Fidelity 401(k) accounts with a balance of $1 million or more hit a record of 168,000 in 2018, up 41 percent from 2017.
Yet many 401(k) users could be losing out on hundreds each year, and thousands of dollars or more over time by not taking full advantage of an employer match.
It's the first thing that comes to mind for Eric Roberge, a CFP and founder of Beyond Your Hammock, when asked what he sees as the biggest mistake people make when saving for retirement.
"My first response is not receiving the employer's matching contribution," he tells CNBC Make It. "If you have a 401(k) at work and you choose to open a Roth IRA, and your employer's willing to give you 100 percent of the first 5 percent that you put in your 401(k), you're missing out on free money."
Here's what he means: When companies offer a 401(k) match, they agree to kick in whatever contribution you make up to a certain amount, so if your employer offers a 5 percent match and you contribute 5 percent of your salary, the equivalent of 10 percent of your salary goes into the tax-advantaged account.
Yet one in five people don't contribute enough to get the full match, according to data from benefits administrator Alight Solutions. Fidelity came to the same conclusion in 2017.