401k Plan:
Definition, Comparison & Benefits

A 401(k) plan is an employer-sponsored retirement savings plan that allows employees to contribute a portion of their wages to individual accounts, with contributions made through payroll deductions and invested in various types of mutual funds. Named after the section of the Internal Revenue Code that created it, a 401(k) offers special tax benefits where contributions can be made on either a pre-tax or after-tax basis depending on the type of plan chosen. The plan was first implemented in 1978 and has since become one of the most popular retirement savings tools in the United States, with approximately 70 million Americans using one to invest money for retirement.

401(k) plans are offered by private-sector employers as part of their benefits package to attract and retain workers. Eligibility typically requires being at least 21 years old and having completed one year of service with the company, though many employers have less restrictive requirements. Once enrolled, employees can choose from investment options selected by the plan sponsor, which may include mutual funds, collective investment trusts, stable value funds, and target-date funds that automatically rebalance to become more conservative as retirement approaches.

Related terms: defined contribution plan, Roth 401(k), traditional 401(k), employer match, 403(b) plan, IRA

For 2026, employees can contribute up to $24,500 in pre-tax or Roth contributions to their 401(k) accounts. Employees who are at least 50 years old at any time during the year are allowed additional catch-up contributions of $8,000, bringing their total potential contribution to $32,500. A special provision for employees aged 60 to 63 allows an additional $3,750 on top of the standard catch-up amount, for a maximum of $35,750.

There is also an overall contribution limit that applies to combined employee and employer contributions. For 2026, this limit is $72,000 or 100% of the employee's compensation, whichever is lower. If the employee exceeds the annual contribution limit, the excess contributions and their earnings must be withdrawn or corrected by April 15 of the following year to avoid being taxed twice on the same money.

According to the SECURE 2.0 Act, starting in 2026, catch-up contributions for high earners whose FICA wages exceed $150,000 in the previous tax year must be designated as Roth after-tax contributions. If an employer's plan does not offer a Roth contribution feature and the employee falls under this high-earner rule, the employee will not be able to make catch-up contributions to that plan.

Traditional and Roth 401(k) plans differ primarily in their tax treatment of contributions and withdrawals. A traditional 401(k) allows employees to contribute pre-tax dollars, which reduces their taxable income in the year of contribution. These contributions are not taxed until withdrawal, at which point they are subject to ordinary income tax. This structure benefits employees who are currently in a high tax bracket but expect to be in a lower bracket during retirement.

A Roth 401(k) operates in the opposite manner. Contributions are made with after-tax dollars, meaning employees pay taxes on the money before it goes into the account. However, qualified withdrawals from a Roth 401(k) are tax-free, provided the account has been held for at least five years and distributions begin after age 59½, death, or disability. Unlike Roth IRAs, Roth 401(k) plans have no upper-income limit capping eligibility, making them accessible to high earners who are disqualified from contributing to a Roth IRA.

Both types of 401(k) plans are subject to the same annual contribution limits and may offer the same investment options. Employees can contribute to both traditional and Roth 401(k) accounts in the same year, but the total of those two contribution amounts must not exceed the contribution limit. Employer matching contributions must be made on a pre-tax basis, regardless of whether the employee's contributions are traditional or Roth.

Employer matching is a provision where companies contribute to employees' 401(k) accounts based on the amount the employee contributes. This matching contribution represents additional compensation that helps employees save more for retirement without requiring extra effort on their part. According to the 2024 How America Saves Report, the average employer 401(k) match is 4.6% of an employee's salary.

Matching formulas vary by employer. A partial match occurs when an employer agrees to match a certain percentage of employee contributions, often 50%, up to a specific percentage of salary, often 6%. For example, if an employee earning $100,000 contributes 6% of compensation ($6,000), an employer offering a 50% match would contribute $3,000. A dollar-for-dollar match (100% match) means the employer matches employee contributions at the full rate up to a particular percentage of compensation. Some companies also offer non-elective contributions that are made regardless of whether or how much the employee contributes.

Many employers require employees to wait for a certain period before employer contributions vest, meaning they become the employee's property to keep. This vesting schedule is an important consideration before changing jobs, as leaving before contributions are fully vested can result in forfeiting some or all of the employer's contributions. Financial advisors often recommend contributing at least enough to receive the full employer match, as it represents an immediate return on investment.

The Internal Revenue Code imposes restrictions on when money can be withdrawn from a 401(k) plan without penalties. Generally, participants may begin to withdraw money after reaching age 59½ without paying the 10% early withdrawal penalty. Withdrawals taken before this age are subject to both ordinary income tax and a 10% penalty tax, except in specific circumstances defined by the IRS.

Exceptions to the 10% early withdrawal penalty include distributions after both reaching age 55 and separating from employment, total and permanent disability, death, substantially equal periodic payments under section 72(t), qualified domestic relations orders, unreimbursed medical expenses exceeding 7.5% of adjusted gross income, qualified military reservist distributions, and distributions for financial hardship. The SECURE 2.0 Act added new exceptions for domestic abuse, emergency expenses up to $1,000, and disaster relief up to $22,000.

Required minimum distributions (RMDs) must begin by April 1 of the calendar year after turning age 73, or April 1 of the calendar year after retiring, whichever is later. This age will increase to 75 in 2033. The RMD is calculated based on the account balance and life expectancy according to IRS tables. Failure to take the required minimum distribution results in a penalty of 25% of the amount that should have been withdrawn. Roth 401(k) accounts were exempt from RMDs for the owner starting in 2024, though beneficiaries who inherit Roth accounts must still take RMDs.

Many 401(k) plans allow participants to borrow money from their accounts rather than taking a taxable distribution. The loan principal is not considered taxable income and is not subject to the 10% early withdrawal penalty as long as it is repaid according to IRS regulations. Section 72(p) of the Internal Revenue Code requires that loans be for a term no longer than five years, except when used for the purchase of a primary residence, that a reasonable rate of interest be charged, and that substantially equal payments be made at least every calendar quarter.

The interest on a 401(k) loan is paid back into the participant's own 401(k) account rather than to a financial institution, essentially becoming additional after-tax contributions. While the movement of the loan principal is tax-neutral when properly repaid, the interest portion creates a tax issue because it is paid with after-tax funds but does not increase the after-tax basis in the account. Upon distribution or conversion of those funds, the owner will have to pay taxes on the interest funds a second time.

If an employee does not make loan payments according to plan rules or IRS regulations, the outstanding loan balance is declared in default. A defaulted loan becomes a taxable distribution to the employee in the year of default, subject to ordinary income tax and the 10% early withdrawal penalty if applicable. Additionally, if the employee changes or leaves their job, they may be required to repay the loan in full within a very short time frame, or face taxes and penalties on the unpaid balance.

When leaving a job, employees have several options for managing their 401(k) accounts. They can leave the money in their former employer's plan if the plan allows this and the account balance meets minimum requirements, roll the funds over to their new employer's 401(k) plan, roll the funds into an individual retirement account (IRA), or take a cash distribution. Each option has distinct advantages and disadvantages that should be carefully considered.

Rollovers between eligible retirement plans can be accomplished through either a direct rollover or an indirect rollover. A direct rollover occurs when the plan sponsor sends the account balance directly to the new plan, with no taxes withheld from the transfer amount. An indirect rollover involves the plan sending a check to the participant, with 20% withheld for federal taxes and possibly state taxes. The participant then has 60 days to deposit the full amount, including the withheld taxes, into the new account to avoid it being treated as a taxable distribution.

Leaving assets in a former employer's plan may be beneficial if that plan offers low-cost investment options or unique funds not available elsewhere. Rolling over to a new employer's 401(k) can help consolidate retirement savings and simplify account management. Rolling over to an IRA typically provides the widest selection of investment options and greater control over investment strategy. Taking a cash distribution before age 59½ results in ordinary income tax plus a 10% penalty on the withdrawn amount, making this the least favorable option in most circumstances.

The IRS defines highly compensated employees (HCEs) to help ensure that 401(k) plans benefit all employees, not just those with higher incomes. For 2025, an HCE is an employee who earned more than $160,000 in the prior year or who owned more than 5% of the business at any time during the year or the preceding year. Employers can elect to limit the top-paid group to the top 20% of employees ranked by compensation.

Non-discrimination testing compares the average deferral percentage (ADP) of HCEs to that of non-highly compensated employees (NHCEs). The ADP of all HCEs as a group cannot be more than two percentage points greater than the ADP of all NHCEs as a group. When a plan fails the ADP test, it must either return excess contributions to the HCEs to lower their average deferral percentage, or process a qualified non-elective contribution (QNEC) to some or all NHCEs to raise their average deferral percentage to a passing level.

Safe harbor provisions allow companies to be exempted from ADP testing by making certain employer contributions. Safe harbor contributions can take the form of a match, generally totaling 4% of pay, or a non-elective profit sharing contribution totaling 3% of pay. Safe harbor contributions must be 100% vested immediately with immediate eligibility for employees, and employers must notify all eligible employees of the opportunity to participate in the plan.

Automatic enrollment allows employers to enroll employees in 401(k) plans by default, requiring employees to actively opt out if they do not want to participate. This approach reverses the traditional model where employees had to opt in to participate. Companies offering automatic enrollment must choose a default investment fund and default savings rate for employees who are enrolled automatically, though employees can select different funds and rates or opt out completely.

The Pension Protection Act of 2006 made automatic enrollment safer for employers by establishing qualified default investment alternatives (QDIAs). Prior to this act, employers were held responsible for investment losses resulting from automatic enrollments. QDIAs provide sponsors with fiduciary relief when participants are automatically enrolled in approved default investments. Under Department of Labor regulations, three main types of investments qualify as QDIAs: lifecycle funds, balanced funds, and managed accounts.

Employers can attempt to enroll non-participants as often as once per year, requiring those non-participants to opt out each time. Employers can also choose to implement automatic escalation, which increases participants' default contribution rates over time, encouraging them to save more without requiring active decision-making. These features are designed to encourage high participation rates and help employees build adequate retirement savings.

401(k) plans charge fees for administrative services, record-keeping services, investment management services, and sometimes outside consulting services. These fees can be charged to the employer, the plan participants, or to the plan itself, and can be allocated on a per-participant basis, per plan, or as a percentage of plan assets. For 2011, the average total administrative and management fees on a 401(k) plan was 0.78 percent or approximately $250 per participant, though small businesses often face higher plan fees.

Plan fees can substantially reduce retirement savings over time due to the compounding effect of costs. The United States Supreme Court ruled in 2015 in Tibble v. Edison International that plan administrators could be sued for excessive plan fees and expenses. In that case, the Court criticized a large company for placing plan investments in retail mutual fund shares instead of lower-cost institutional class shares.

Participants should review their plan's fee disclosure documents to understand what fees are being charged and how they impact investment returns. Fees are typically disclosed in account statements and in annual fee disclosure notices required by the Department of Labor. Understanding these costs helps participants evaluate their plan's investment options and make informed decisions about their retirement savings strategy.

A 401(k) plan is often compared to 4 related retirement savings vehicles:

401(k) Plan vs. IRA

A 401(k) is tied to employment and offers higher contribution limits ($24,500 for 2026) with potential employer matching contributions. An IRA is established independently by individuals with a lower contribution limit ($7,500 for 2026) but typically offers a far wider selection of investment options since the account holder can choose any IRA provider and is not restricted to employer-selected investments. IRAs also provide more flexibility in withdrawal options and conversion strategies, though they lack the benefit of employer contributions.

401(k) Plan vs. 403(b) Plan

Both 401(k) and 403(b) plans are defined contribution retirement plans with identical contribution limits and similar tax treatment. The primary difference is the type of employer offering the plan: 401(k) plans are provided by for-profit companies while 403(b) plans are offered by nonprofit organizations, public schools, and certain religious organizations. Both plan types can offer traditional pre-tax and Roth after-tax contribution options, and both are subject to the same withdrawal rules and required minimum distribution requirements.

401(k) Plan vs. 457(b) Plan

A 457(b) plan is offered by state and local government entities and has the same contribution limits as 401(k) plans. The key advantage of 457(b) plans is that withdrawals before age 59½ are not subject to the 10% early withdrawal penalty that applies to 401(k) distributions, as long as the participant has separated from service. Government employers established after May 1986 are barred from offering 401(k) plans and must use 457(b) plans instead. Both plan types allow for traditional and Roth contributions where available.

401(k) Plan vs. Defined Benefit Pension

A defined benefit pension promises a specific monthly benefit at retirement, calculated using a formula that considers factors such as salary and years of service. The employer bears all investment risk and is responsible for funding the promised benefits, which are protected by federal insurance through the Pension Benefit Guaranty Corporation (PBGC). In contrast, a 401(k) is a defined contribution plan where the employee and potentially the employer contribute to an individual account, and the final retirement benefit depends on total contributions and investment performance. The employee bears the investment risk in a 401(k), but also has more control over investment choices and portability when changing jobs.