For nearly a decade, Lena assumed a piece of every paycheck went into her 401(k). However, when she checked her company’s retirement portal, she noticed something was seriously off.

There wasn’t nearly as much money in her 401(k) to account for her time at the company and the market’s growth. As she double-checked statements and details in her profile, Lena realized what was at the root of the problem: There was a typo on her birth date.

Apparently, when Lena was hired some ten years ago, it appeared that she was 14 rather than 24. Because of that error, the company’s automated system marked her as “ineligible” for years of 401(k) participation.

Imagine the result. She would have missed thousands of contributions and the compounded investment growth that would have come with them — all because of one tiny data entry error.

A 401(k) is supposed to be straightforward to understand and implement. Here’s the basic structure: The employer sets up a tax-deferred account, employees choose how much to contribute from each paycheck and that money gets invested automatically.

Most companies also offer a match, which is basically free money that employers contribute based on how much workers put in.

For example, say a company matches 50% of contributions up to 5% of an employee’s salary. If someone earns $70,000 and contributes $3,500 (5%), they’d be maximizing the company match, getting another $1,750 on which to earn interest.

But, there are 401(k) eligibility rules.

Federal law allows employers to set waiting periods before new employees can participate, but the IRS policy is one year of service. (1) The IRS also has a minimum age requirement of 21. Once employees meet those criteria, they should get enrolled and receive all the contributions they’re eligible for.

That’s where Lena’s situation went sideways. Because her starting age was incorrect, the system flagged her as too young to participate in the early years. Every payroll cycle, her employer’s contribution system skipped over her, and nobody caught it because the automatic program wasn’t built to question its own data.

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It’s understandable how Lena could have gotten into her predicament, but the question now is whether someone can reclaim missed retirement money after such an error.

Step one is to build a case with tons of official evidence. We’re talking about pay stubs, benefit statements and any onboarding documents that might show a mistaken detail, like birth date, and the 401(k) eligibility requirements.

Next, you’d want to contact your HR department in an email or letter with a polite yet firm message explaining the missing 401(k) contributions and data error. Ask for a full audit of the account and payroll history.

Remember that under the Employee Retirement Income Security Act (ERISA), employers have a fiduciary duty to maintain accurate plan records and correct errors. (2)

If the company confirms the mistake, it will likely need to make a “plan correction.” That means depositing the missed contributions (both the employee’s and the employer’s match) into the account, plus an amount to compensate for lost investment growth.

Hopefully, the case gets resolved at this point, but it’s possible to escalate it to the U.S. Department of Labor’s Employee Benefits Security Administration (EBSA). (3) This agency has the tools to investigate and compel employers to fix mistakes. Enlisting the help of a financial advisor or employment attorney can also help in extreme cases.

While it’s nice to know there are resources to help reclaim retirement savings, it’s always best to prevent a 401(k) mess up in the first place.

The most effective way to minimize the chances of this situation is to be super vigilant about checking 401(k) contributions — from the very first pay stub. It also helps to review statements at least once a quarter and double-check personal information like date of birth, hire date and address.

It may sound trite, but awareness is the best defense. Knowing all the details of your 401(k) plan and following the money rather than trusting automated systems are the best strategies for maximizing your retirement savings.

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IRS (1); U.S. Department of Labor (2); Employee Benefits Security Administration (3)

This article provides information only and should not be construed as advice. It is provided without warranty of any kind.