Employer 401(k) Match, Explained With the Actual Numbers
How employer matching contributions work under IRS rules, with a worked example showing exactly how much free money different contribution levels unlock.
An employer match is one of the few places in personal finance where the phrase "free money" is not an exaggeration. According to the IRS, matching contributions are money your employer adds to your retirement plan account specifically because you contributed from your own salary, and the IRS is explicit that these contributions do not reduce the amount you're allowed to contribute yourself. Understanding the mechanics, not just the general idea, is what lets you capture the full match instead of leaving part of it on the table.
What a match formula actually looks like
The IRS describes a common structure: the employer matches a percentage of your contribution, up to a specified percentage of your salary. Their own example is 50% of your contributions, up to 5% of your annual salary. That phrase, "up to 5% of your salary," is the part people misread. It does not mean you get matched on the first 5% of whatever you contribute; it means the match formula only looks at contributions up to 5% of your salary, and ignores anything you contribute beyond that point for match purposes.
The IRS's own worked examples, and what they mean
The IRS publishes two examples directly. Someone earning $30,000 a year who contributes $1,200 (4% of salary) gets a 50% match on that $1,200, adding $600. Someone who instead contributes $2,000 (about 6.7% of salary) does not get a 50% match on the full $2,000. Because the formula only matches up to 5% of salary ($1,500 in this case), the match caps at 50% of $1,500, or $750, not 50% of $2,000.
Here is the same logic run on a different salary, to show how it generalizes:
| Salary | Employee contributes | Employer 50% match (up to 5% of salary) |
|---|---|---|
| $55,000 | 3% ($1,650) | $825 |
| $55,000 | 5% ($2,750) | $1,375 |
| $55,000 | 8% ($4,400) | $1,375 |
Notice that contributing 5% and contributing 8% produce the exact same match amount, $1,375, because the match formula caps out at 5% of salary regardless of how much more you put in beyond that. The extra 3% in the last row still grows for you, tax-advantaged, but it stops attracting additional employer money. This is the single most useful number to know from your own plan: the percentage of salary at which the match formula stops increasing.
Match types: discretionary, mandatory, and non-elective
The IRS distinguishes between a few structures that look similar on the surface but behave differently. Matching contributions can be discretionary, meaning the employer can choose to offer them in some years and not others, or mandatory, as is the case in SIMPLE IRA plans and Safe Harbor 401(k) plans. Separately, some employers make non-elective contributions, which go into every eligible employee's account regardless of whether that employee personally contributes anything at all. A Safe Harbor plan, specifically, might offer either a guaranteed match formula or a flat 3% non-elective contribution to all eligible employees every year, by the plan's own design.
Knowing which category your plan falls into matters because a discretionary match is not guaranteed to repeat next year, even if it showed up on every past paycheck, while a Safe Harbor match formula is a contractual commitment the employer must honor as part of the plan's design.
How matching contributions are taxed
Matching contributions follow the same tax treatment as the rest of a traditional 401(k): they grow tax-free while inside the plan and are only taxed when you withdraw them, typically in retirement. They do not count as taxable income to you in the year they're contributed, and the IRS is explicit that they do not reduce the amount you are personally allowed to defer from your own salary into the plan, within the IRS's own annual limits on total contributions.
How to find your plan's specific match formula
The IRS points to one authoritative source for the details of your specific plan: the plan document and summary plan description your employer provides. That document will state exactly how long you have to work before matching contributions vest (become permanently yours), the specific matching formula, and the contribution percentage needed to capture the maximum match available. Since formulas vary by employer, the general example above is a template for understanding the mechanics, not a substitute for checking your own plan's actual numbers.
Key takeaways
- A typical match formula, per IRS guidance, matches a percentage of your contribution up to a capped percentage of your salary; contributions beyond that cap still grow but no longer draw additional match money.
- In the IRS's own example, contributing more than the capped percentage (6.7% instead of 5%) did not increase the match beyond what 5% alone would have produced.
- Matches can be discretionary (employer's year-to-year choice), mandatory under SIMPLE or Safe Harbor plan rules, or offered as a non-elective contribution unrelated to your own deferrals.
- Matching contributions grow tax-free until withdrawal and do not reduce how much you are personally allowed to contribute from your salary.
- Your plan's summary plan description, not a general example, has the exact match percentage, salary cap, and vesting schedule that apply to you.
Find the exact percentage of your own salary where your plan's match formula stops increasing, and treat contributing up to that number as the non-negotiable first move before any other saving or investing decision.