If your employer offers a 401(k) with a matching contribution and you're not contributing enough to capture the full match, you are leaving part of your compensation on the table every single paycheck. That's not a figure of speech. The match is money your employer has agreed to give you, conditional only on you saving some of your own. Declining to capture it is declining part of your salary.
Beyond the match, the 401(k) is the most tax-advantaged savings vehicle available to most workers ??? combining a significant annual contribution limit with tax benefits that compound dramatically over decades. This guide explains how it all works.
What Is a 401(k)?
A 401(k) is an employer-sponsored retirement savings account that lets you contribute a portion of each paycheck before or after taxes, with the money invested in a menu of funds chosen by your employer. The name comes from Section 401(k) of the Internal Revenue Code ??? the provision that created this account type in 1978.
The defining features:
- Contributions come from your paycheck ??? You elect a percentage or dollar amount to defer; it moves automatically before you see it
- High annual contribution limits ??? Far higher than an IRA, allowing significant tax-advantaged saving
- Employer matching ??? Many employers add contributions of their own, tied to how much you save
- Tax advantages ??? Either traditional (pre-tax) or Roth (after-tax), each with distinct benefits
- Investment growth is tax-deferred or tax-free ??? Depending on account type, you don't pay tax on gains until withdrawal (or never, with Roth)
Traditional 401(k) vs. Roth 401(k)
Many employers now offer both traditional and Roth options within the same 401(k) plan. The choice between them is fundamentally a bet on your future tax rate:
| Feature | Traditional 401(k) | Roth 401(k) |
|---|---|---|
| Contributions | Pre-tax (reduces taxable income today) | After-tax (no tax break today) |
| Growth | Tax-deferred | Tax-free |
| Withdrawals in retirement | Taxed as ordinary income | Tax-free (if rules met) |
| Required Minimum Distributions | Yes, starting at age 73 | No (starting 2024, per SECURE 2.0) |
| Best if you expect | Lower tax rate in retirement | Higher tax rate in retirement |
For most people early in their career ??? when income (and thus tax rate) is lower ??? the Roth 401(k) is often the better choice. Tax-free growth over 30–40 years is extraordinarily powerful. Higher earners in peak earning years often benefit more from the traditional 401(k)'s immediate tax deduction.
2025 Contribution Limits
| Contribution Type | 2025 Limit |
|---|---|
| Employee elective deferrals (under 50) | $23,500 |
| Catch-up contributions (age 50–59 and 64+) | +$7,500 (total $31,000) |
| Super catch-up (age 60–63, new per SECURE 2.0) | +$11,250 (total $34,750) |
| Total including employer contributions | $70,000 |
These limits are indexed to inflation and typically increase by $500 increments most years. The IRS announces the following year's limits in October or November.
How Employer Matching Works
Employer matching is an additional contribution your employer makes to your 401(k), tied to your own contributions. The match formula varies by employer ??? here are the most common structures:
100% match up to X% of salary
The most generous and straightforward formula. "100% match up to 4% of salary" means: for every dollar you contribute up to 4% of your salary, your employer adds another dollar. At $80,000/year, contributing 4% ($3,200) earns you a $3,200 match ??? $6,400 total in your account.
50% match up to X% of salary
"50% match up to 6% of salary" means your employer adds 50 cents for every dollar you contribute, up to 6% of your salary. At $80,000, contributing 6% ($4,800) earns a $2,400 match. You need to contribute 6% to capture the full match ??? contributing only 3% leaves match money on the table.
| Common Match Formula | Your Contribution to Capture Full Match | Effective Immediate Return |
|---|---|---|
| 100% up to 3% | 3% of salary | 100% |
| 100% up to 4% | 4% of salary | 100% |
| 50% up to 6% | 6% of salary | 50% |
| 100% up to 3%, 50% on next 2% | 5% of salary | 60–100% blended |
The Long-Term Power of a 401(k): Real Numbers
The combination of tax advantages, employer matching, and decades of compound growth makes the 401(k) extraordinarily powerful. Consider two employees both earning $70,000:
| Employee A | Employee B | |
|---|---|---|
| Own contribution | 6% ($4,200/yr) | 6% ($4,200/yr) |
| Employer match (50% up to 6%) | $2,100/yr | $0 (no employer match) |
| Total annual investment | $6,300 | $4,200 |
| Balance after 30 years at 7% | $631,000 | $421,000 |
| Difference | $210,000 from the employer match alone | |
Use our Retirement Calculator to model your specific contribution rate, employer match, salary, and time horizon to see your projected balance.
401(k) Withdrawal Rules
- Normal retirement age: 59?? ??? withdrawals after this age are penalty-free
- Early withdrawal penalty: 10% penalty on withdrawals before 59??, plus ordinary income tax (traditional) ??? avoid if at all possible
- Required Minimum Distributions (RMDs): Traditional 401(k)s require minimum withdrawals starting at age 73
- Loans: Many plans allow borrowing from your 401(k) ??? generally inadvisable as it interrupts compound growth and creates repayment risk
- Hardship withdrawals: Available for specific qualifying financial emergencies; still subject to taxes and often penalties
Project Your Retirement Balance
The Retirement Calculator models your 401(k) growth with any contribution rate, employer match, salary, and expected return over your working years.
Traditional or Roth 401k? Check Your Bracket First
Pre-tax 401k contributions reduce your taxable income now. Use the Tax Bracket Calculator to see exactly how much your contribution saves you this year -- and whether Roth makes more sense.