John Fuchs was checking his 401(k) account online one afternoon when he saw something that seemed amiss. Listed along with his regular contributions was a $48 charge, in red.

That's odd, he thought.

Why would anyone be taking money out of his account?

After a flurry of phone calls and e-mails, Fuchs learned that the $48 deduction was no mistake. The money was paid to an outside business that enrolls employees in his company's 401(k) plan, mails quarterly account statements and handles other administrative tasks.

Fuchs knew the mutual funds he'd chosen charged fees for investing his money. He didn't know that overhead costs were also being taken out of his account. They now cost him about $500 a year.

Because the administrative fee is a percentage of his balance, he will pay more and more as his savings grow. Fuchs figures that by the time he retires, it will have cost him more than $316,000 in direct charges and lost investment returns.

"I think a lot of people out there pay this fee but don't know it," said Fuchs, 38, an information technology manager for an engineering company in Exton, Pa. "To the average employee, it's totally invisible."

As many employers scrap their traditional pensions and doubts grow about the future of Social Security, Americans' hopes for a secure retirement depend more than ever on their 401(k)s. About 44 million workers have more than $2 trillion invested in these accounts.

Yet unknown to many of them, obscure fees and deductions are quietly eroding the value of their nest eggs. In many cases, employers could bargain for lower charges but do not.

Mutual fund management fees are the biggest expense. But they are prominently disclosed, have attracted wide publicity and have been declining as fund providers compete for customers.

Administrative fees are another matter. They usually don't show up on quarterly or annual statements. Brochures touting the benefits of 401(k) investing rarely mention them. Employees have to work hard to find out how much they're paying — for instance, by scouring their plan's Web site for a record of all activity in their accounts.

Plan consultants and providers collect their cut in varied ways. Some take a percentage of each employee's account balance. That's the charge Fuchs stumbled upon. Others collect a commission from insurance companies that run 401(k) plans.

When mutual fund companies manage 401(k)s, they often absorb overhead costs in return for the chance to give most of the "shelf space" to their own funds. They get their money back through fund management fees.

What's more, fund providers frequently offer 401(k) participants the same retail mutual funds they sell to the general public, not the low-fee alternatives designed for big groups of customers.

Employees tenacious enough to demand information about fees from benefits departments or 401(k) administrators often complain that they can't get straight answers.

Because of outdated federal disclosure rules, publicly available records on fees often reveal only a fraction of the money leaking out of retirement accounts.

"It's very difficult for the average participant to determine what the total expenses are, how those expenses measure up, and who exactly is getting paid and how much," said Bud Green, of Fortress Wealth Management Inc., a 401(k) consulting company in Santa Monica, Calif.

Workers who save conscientiously take a disproportionate hit because fees are typically a percentage of their account balances. Someone with $100,000 pays 10 times as much as a co-worker with $10,000, even though it costs about the same to administer the two accounts.

The peculiar structure of 401(k)s leaves employees with little or no voice. Employers sponsor the plans and hire the providers and administrators. But workers pay most of the fees.

Employees can raise a stink about the charges, but they're stuck with whatever plan their company offers.

"People can be paying thousands of dollars in fees if they've been in their 401(k) plans for years," said John Turner, a senior policy adviser at the AARP Public Policy Institute. "They can be paying thousands of dollars more than they need to be paying."

401(k)s were an accidental byproduct of a 1978 tax law.

Shortly after the law took effect, a few benefits consultants realized that subsection 401(k) — intended to clarify the tax status of corporate profit-sharing plans — allowed workers to accumulate tax-deferred savings through payroll deductions.

In the early days, employers picked up most of the administrative costs of the plans. That changed as mutual fund companies and insurers sought a larger share of 401(k) business.

Those companies offered to handle every aspect of the retirement plans, including administration. In exchange, they would have a captive audience for their investment products.

Employers liked the new arrangement because it greatly reduced their costs. The losers were employees.

In 1988, 87 percent of U.S. employers paid all 401(k) administrative costs. Today, only about 25 percent do. The rest have shifted some or all of those expenses to workers, said Pam Hess, a 401(k) expert at Hewitt Associates, a benefits consulting company that also administers retirement plans.

As a result, employers have little incentive to hold down 401(k) costs. A 2004 Hewitt survey found that about half of employers haven't even tried to figure out what their workers are paying in fees.

401(k) GLOSSARY