401(k)

A 401(k) plan is the cornerstone of workplace retirement saving in the United States, taking its name from Section 401(k) of the Internal Revenue Code. Employees elect to defer a percentage of each paycheck directly into their account before the money ever hits their bank, reducing their current taxable income in the process. The invested funds grow tax-deferred, meaning you pay no federal income tax on gains, dividends, or interest until you withdraw the money in retirement.

For 2025, the employee elective deferral limit is $23,500. Workers aged 50 or older may make an additional 'catch-up' contribution of $7,500, bringing their ceiling to $31,000. SECURE Act 2.0 introduced an enhanced catch-up for those aged 60-63: $11,250 in 2025, making their total limit $34,750.

Many employers sweeten the deal with a matching contribution — a common formula is 50 cents for every dollar the employee contributes, up to 6% of salary. This match is essentially free money and represents an immediate 50% return on the contributed dollars. The combined limit from all sources (employee deferrals plus employer contributions) is $70,000 for 2025, or $77,500 for those 50 and older.

Participants typically choose from a menu of mutual funds and target-date funds curated by the plan sponsor. The investments grow inside a protected account governed by ERISA (the Employee Retirement Income Security Act), which sets fiduciary standards to protect participants. Withdrawals before age 59½ are generally subject to a 10% early withdrawal penalty on top of ordinary income tax, with limited exceptions such as disability or substantially equal periodic payments under Rule 72(t).

Roth 401(k) subaccounts, now available in most plans, allow after-tax contributions that grow tax-free, with qualified withdrawals in retirement completely free of federal income tax. Starting in 2024, employer matching contributions can also be directed into Roth accounts. The 401(k) remains the most widely used private retirement vehicle in America, holding trillions in assets across tens of millions of participant accounts.

Contribution Limits for 2025 reflect adjustments for inflation. The employee elective deferral ceiling sits at $23,500. The standard age-50 catch-up adds $7,500, and the new SECURE Act 2.0 enhanced catch-up for participants aged 60, 61, 62, and 63 raises that additional amount to $11,250, producing a total deferral of $34,750 for those in that narrow age band. The overall Section 415 ceiling — covering all contributions from employee deferrals plus employer matching and profit-sharing — is $70,000, or $77,500 for participants aged 50 and older using the standard catch-up. Understanding these limits allows workers to maximize their tax-deferred savings space each calendar year, especially during peak earning years when maximizing contributions delivers the largest present-year tax benefit.

Several common 401(k) mistakes reduce the long-term value of these accounts. The most costly is contributing only enough to capture the employer match and stopping there, forgoing years of additional tax-deferred compounding. A second frequent error is selecting high-expense mutual funds from the plan menu when lower-cost index alternatives are available in the same plan — a 1% difference in annual expenses compounds into a dramatically smaller account balance over 30 years. Third, cashing out a 401(k) when changing jobs — rather than rolling it into a new employer plan or an IRA — triggers income tax, the 10% early withdrawal penalty, and a permanent loss of that capital's tax-sheltered growth potential. Fourth, neglecting to update beneficiary designations after marriage, divorce, or the birth of a child can lead to unintended inheritance outcomes regardless of what a will says.

Comparing a 401(k) to an IRA reveals complementary strengths rather than a simple hierarchy. The 401(k) offers a contribution ceiling more than three times higher than the IRA limit, making it the primary vehicle for high-volume savers. Employer matching contributions are unique to workplace plans and have no IRA equivalent. However, IRAs — whether Traditional or Roth — offer a far broader investment menu than most employer plans, which are typically restricted to 20-30 pre-selected funds. IRAs also carry no plan-specific fees and allow the account holder to choose any custodian. For most workers, the optimal approach is sequential: contribute enough to the 401(k) to capture the full employer match first, then fund a Roth or Traditional IRA to its annual limit, and finally return to the 401(k) to contribute additional pre-tax or Roth dollars up to the plan maximum.

401(k) Loan Risks: Most 401(k) plans permit participants to borrow up to the lesser of $50,000 or 50% of their vested account balance, repayable over five years with interest (the interest is paid back to your own account). While a 401(k) loan avoids the immediate income tax and 10% penalty of a withdrawal, it carries significant risks that are frequently underestimated. First, the borrowed funds are not invested during the loan period, creating an opportunity cost on the forgone market growth. Second, if the participant leaves the employer — voluntarily or involuntarily — the outstanding loan balance typically becomes due in full within a short period (often 60 to 90 days or by the tax return deadline). Failure to repay the balance converts it into a taxable distribution subject to income tax and, for those under 59½, the 10% early withdrawal penalty. Third, many participants repay the loan with after-tax dollars, then pay tax again on those dollars in retirement — creating effective double taxation on the loan amount.

Changing Jobs: Rollover Options: When leaving an employer, participants face four choices for their 401(k) balance. First, leave it in the former employer's plan — permissible if the balance exceeds $5,000 and the plan allows it, and convenient if the plan has excellent low-cost investment options. Second, roll it into the new employer's plan — consolidates accounts and maintains simplicity, but only advisable if the new plan offers quality investment options. Third, roll it into an IRA — provides the broadest investment flexibility and typically no management fees; the preferred choice for most departing employees. Fourth, cash it out — triggers ordinary income tax, the 10% early withdrawal penalty for those under 59½, and mandatory 20% federal withholding on the distribution; the most costly option by far and one that should almost never be chosen when alternatives exist. A direct rollover (instructing the plan to send funds directly to the new custodian) is always preferable to an indirect rollover to avoid the 20% withholding trap.