The 401(k) plan is one of the most popular ways for workers to build up their nest eggs for retirement. As of June 2017, 55 million Americans held an estimated $5.1 trillion in assets in 401(k) plans. Whether you’re already enrolled or planning to enroll in your employer-sponsored retirement plan, there are several details that you should find out to make the most of it. Let’s review some key 401(k) questions you need to ask your employer. (See also: 5 Dumb 401(k) Mistakes Smart People Make)

1. When am I eligible to make contributions?

Different plans have different rules. You shouldn’t assume that the same rules from your previous workplace retirement savings plan will apply to that of your current job. Some plans may require you to wait at least six to 12 months before you can contribute to your account, while others may allow you to do so right away. In a review of 4.4 million 401(k) plans in 2016, Vanguard found 67 percent of plans offered immediate eligibility for employee contributions.

2. Do you offer a company match?

America is experiencing very low unemployment levels. In October 2017, the Bureau of Labor Statistics reported the national unemployment rate stood at 4.1 percent, with some states reaching even lower rates (North Dakota and Colorado recorded 2.5 percent and 2.7 percent, respectively, that same month). Looking to retain and attract talent, more and more employers match employee contributions to their retirement accounts. In Vanguard’s How America Saves 2017 report, 94 percent of employers offered matching 401(k) contributions in 2016, up from 91 percent in 2013. After you find out how much of a match your workplace offers, be sure to contribute at least up to that amount. If you don’t, you’ll be leaving free money on the table.

3. What type of formula do you use for matching contributions?

In 2016, there were over 200 different ways in which employers matched their employee contributions, according to Vanguard. By far the most common formula (70 percent of plans) is 50 cents for every dollar up to 6 percent of your pay. Assuming that you make $50,000, this would mean that your employer would contribute up to $1,500 if you were to contribute $3,000 to your 401(k).

Here are the next two most common types of matching formulas found in the study:

  • $1.00 per dollar on first 3 percent of pay, then $0.50 per dollar on next 2 percent of pay (22 percent of plans).
  • A dollar cap, often set at $2,000 (5 percent of plans).

It’s important to find out the matching formula used by your…