Not only do you have to find a groove with your tasks, but you also have to navigate office personalities, deal with return-to-office policies, and try to impress your new boss. That’s not to mention the mound of paperwork like signing up for insurance and retirement savings, which for young professionals in particular, can be confusing. But putting it off can quickly result in a major money blunder.

For one woman, that ignorance added up to a six-figure financial mistake.

“I found out, after having worked for my company for many years, that I was leaving behind 100% match on my 401(k),” Teresa Greenip tells Fortune.

After landing a job at a commercial real estate firm, she neglected to take advantage of a retirement savings plan with a match program that in total would have been $60,000 in free money. Had it grown with her contributions at an average return rate, she would have amassed over $500,000 in retirement savings.

Making this “gigantic money mistake” was a wake-up call for Greenip, but it’s a situation that is not all that uncommon. 

Nearly a quarter of all Gen Z employees aren’t enrolled in their company’s 401(k)—that’s three times the rate of millennials, Gen X, and boomers, according to BenefitsPro. Moreover, 12% of Gen Zers neglect to participate in any workplace benefits, double the rate of other generations.

A few small mistakes can compound into millions of dollars left behind

When Greenip graduated from Emory University in 2004, her heart was set on a high-paying career in the corporate finance world. 

She checked all the boxes: she majored in business administration, served as a teaching assistant for tough courses like managerial accounting, and made the dean’s list. However, once she landed a job in commercial real estate, Greenip prioritized paying off her personal and student loans before considering saving for retirement. 

And while prioritizing debt repayment may seem logical, it was exactly where she ran into trouble. Outweighing savings goals, even when retirement seems far away, can come back to hurt later in life.

Gradually investing in a 401(k) can be life-changing by the time retirement arrives—and the earlier you contribute, the greater the compounding. Employers commonly match up to 50% of an employee’s 401(k) contributions, up to a maximum of 6% of their salary. For someone making $80,000 who begins contributing to their 401(k) at age 25, they could gain over $300,000 in employer contributions alone, which can compound over their lifetime into millions of dollars.

Greenip’s oversight is not an uncommon one. While employer match programs may be designed to incentivize workers to contribute to companies’ retirement plans, evidence suggests they only have small effects on participation and savings, according to Vanguard. Only about 54% of employees working at a company with a 401(k) match program are investing at or above the match threshold, meaning millions of Americans are missing out on potentially billions of dollars collectively in free retirement savings.

If you are unsure whether your company has a 401(k) match policy, experts say contact your human resources team as soon as possible. If you haven’t checked on your 401(k) in a while, it is always a good idea to make sure everything is invested properly. 

After maximizing an employer’s match program, one might consider additional retirement savings, like investing in a Roth IRA. According to Boston College’s Center for Retirement Research, their popularity has risen significantly among Gen Zers and millennials—from 6.6% participation? in 2016 to 19.2% in 2022.

A mistake that led to a calling

After realizing her mistake, Greenip decided it was time for a career pivot. She left her lucrative job, obtained her certified financial planner (CFP) certification, and made it her life’s work to guide others on their financial journeys and help them avoid costly mistakes like hers.

Now working as a financial planner at Aspiriant, Greenip says individuals must educate themselves. She herself listened to financial experts like Suze Orman and read investing books. For those who can afford it, Greenip says it’s worth working with a financial advisor since they keep up with ever-changing best practices.

She encourages all individuals to take stock of their inflows and outflows—and then set spending goals for a given year. Only then should you begin taking the baby steps of paying off debt and investing funds in brokerage or retirement accounts.

“All of this advice is not just for the wealthy, but it’s for all of us, and the government has set up the rules to benefit all of us, to encourage us to save and invest,” Greenip says.

“I think everybody can benefit from constantly revisiting their financial strategy,” she adds.

Have you made the best of a financial mistake and are open to sharing your story? Email preston.fore@fortune.com.