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What Is a 401(k)? Contributions, Matching and Vesting
A 401(k) is an employer-sponsored US retirement plan. Employees can direct part of their pay into the plan, and an employer may contribute under its own terms. Understanding contributions, vesting and investments separately makes a benefit statement easier to read.
By Farvenzo Explained · Published 22 October 2026 · Sources checked 22 October 2026
A calculator beside financial paperwork, photographed in 2014. Context for working through contribution and matching examples, not an actual 401(k) account.
Photo: Steve Buissinne · Calculator-385506 1280.jpg / source · CC0 1.0.
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Follow the money
The IRS describes employee salary deferrals and employer contributions as potential sources of plan funding. Employees are fully vested in their own salary deferrals. Employer contributions can follow a vesting schedule.
“Vested” concerns ownership of the money. It is different from whether investments have gained or lost value. A fully vested balance can still move with its underlying investments.
An illustrative matching calculation
Imagine an employer matches 50% of employee contributions up to 6% of eligible pay. With hypothetical annual eligible pay of $50,000, contributing 6% means $3,000 from the employee. The illustrative employer match would be $1,500.
These are invented plan terms to explain the arithmetic. An actual plan may use another formula, define eligible compensation differently or impose a vesting schedule. Read the plan documents before assuming a match applies.
Traditional and Roth are tax treatments
Investor.gov distinguishes a traditional 401(k) option from a Roth option by the timing of the tax benefit. The account’s tax treatment is a separate question from its investment menu.
A plan may offer funds with different risks and charges. Choosing a contribution amount does not automatically choose an investment allocation, and a retirement label does not guarantee returns.
A five-question plan review
Identify the employee contribution, employer formula, vesting rules, available investments and fees. Then examine the rules relevant to a job change or proposed withdrawal. Loans and hardship distributions are not universal substitutes for understanding a plan’s conditions.
Contribution ceilings and tax rules can change by year. We link to the IRS rather than publishing a stale number as a timeless limit. This guide explains the framework without choosing a contribution rate or fund for a particular reader.
Why the question is timely
“What is a 401k” appeared in Google’s worldwide Finance rising queries over the past week. The trend identifies an information need; it does not show that all searchers have access to such a plan.
Read next
See what a Roth IRA is. A Roth IRA is an individual arrangement, while a 401(k) is connected to an employer plan. Similar tax vocabulary should not hide that distinction.
Sources
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