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Everything You Need to Know About 401(k) Plans
From basics to advanced strategies, here's a comprehensive guide to understanding your 401(k) and making the most of every dollar you contribute.
What Is a 401(k)? — 401(k) Information
A 401(k) is an employer-sponsored retirement plan. It enables employees to set separately a portion of their earnings as a pre-tax contribution means they reduce their taxable income and accept paying taxes on their investment growth until they make withdrawals (usually after the age of 59½). A 401(k) plan is named after the section of the U.S. Internal Revenue Code which controls it and is the chief tool used by millions of American workers for their retirement.
A traditional 401(k) plan includes pre-tax contributions, which means you reduce your taxable income. You get investment growth on your contributions without paying any taxes on the increase in value until you withdraw the money in retirement. For 2025, the IRS allows you to contribute up to $23,500 per year ($31,000 if you’re aged 50 or over (Catch-up contributions).
A Roth 401(k) plan is available from many employers. Instead of building pre-tax contributions, you make after-tax contributions. At the time of retirement, withdrawals are completely tax-free as long as they are appropriate. Whether to contribute to a traditional or a Roth 401(k) is dependant on your tax bracket and income in retirement.
General Pros and Cons of a 401(k)
A 401(k) is one of the most powerful retirement tools you can use.
✓ Pros
- Pre-tax contributions reduce your current taxable income
- Investment growth is tax delayed; meaning they grow quicker
- Employer contributions are essentially free money
- Large contribution limit of $23,500 in 2025 vs. IRAs $7,000
- Easy to save, all thanks to automatic contributions
- Some plans offer loans and hardship withdrawals
- Assets are protected by ERISA that is, they are safe from most creditors
✗ Cons
- Early withdrawals will experience a 10% penalty before 59½ and income tax
- Must start Required Minimum Distributions (RMDs) from age 73
- Not many investment options
- Not your personal plan, your employer controls what funds you have available
- Income tax payable on withdrawals
- May not own your employer contributions straight away due to vesting periods
A 401(k) Is a Defined Contribution Plan
A 401(k) is a defined contribution plan rather than a pension (Defined Benefit).
A Defined Benefit plan will offer you with a set amount of income each month in retirement. Mostly, calculated using a formula based on salary history and years of service. Your employer will take on the investment risk.
A Defined Contribution plan (401(k)) means there is no definite amount you will get in retirement. The amount you have in retirement will depend on how much you (and your employer) contributed and how well your investments have performed.
Because the investment risk has been shifted to you, it’s important to know how your assets are distributed, and how much you are contributing. Compounding plays a big part in how much income you will receive in retirement.
Key 401(k) Plan Types
- Traditional 401(k): Pre-tax contributions. Taxed as ordinary income
- Roth 401(k): After-tax contributions. Tax-free eligible withdrawals
- SIMPLE 401(k): Aimed at small businesses
- Safe Harbor 401(k): Employer must contribute
📊 401(k) Investments
Most 401(k) plans will offer a selected group of investment options. Usually these will be mutual funds, index funds or the target date funds. Target date funds will automatically become more traditional as you near retirement. Many 401(k) plans default to target date funds.
More experienced investors may wish to build a modified portfolio. Early in your career you may want to invest heavily in equities. As you near retirement, prefer using glide path that is consider investing more into bonds and stable value funds. Always check the expense ratio of the funds. A 0.5% difference can cost you tens of thousands of pounds over your 30-year career
🤝 Employer Match — Free Money
An employer match is one of the most influential things you can have in your compensation. By contributing to your 401(k), your employer will contribute to your retirement. This is free money! Not taking advantage of an employer match is one of the biggest and most costly mistakes people make.
Common employer matches include 50% to a maximum of 6% or 100% to a maximum of 3%. To receive the full employer match, you must contribute at least the amount to meet the maximum.
Our calculator above will show you what percentage you need to contribute to receive the full amount from your employer. If you can’t save more than the minimum, contribute the minimum amount to receive the employer match. You will effectively be getting 50%-100% return on that amount.
401(k) Vesting Periods — When Employer Contributions Become Yours
Your contributions to your 401(k) will always be 100% vested. However your employer contributions may be subject to a vesting schedule which means that you must stay with the company for a certain period of time to gain 100% ownership. If you leave before you are fully vested you may lose some, or all, of your employer contribution.
It’s important to know your vesting schedule before making any decisions with your job.
Types of Vesting Schedules
The IRS allows employers to use several different vesting structures:
| Year of Service | Cliff Vesting (3-year) | Graded Vesting (6-year) | Immediate Vesting |
|---|---|---|---|
| Year 1 | 0% | 0% | 100% |
| Year 2 | 0% | 20% | 100% |
| Year 3 | 100% | 40% | 100% |
| Year 4 | 100% | 60% | 100% |
| Year 5 | 100% | 80% | 100% |
| Year 6+ | 100% | 100% | 100% |
Cliff vs. Graded Vesting
With cliff vesting, you won’t receive any of your employer contributions until you reach the vesting period (usually 3 years). Once you reach this period you will be 100% vested. If you leave before reaching the vesting period you won’t receive any of your employer contributions.
Graded vesting means you will receive a percentage of your employer contributions over 6 years. Each year you will gain a percentage so even if you leave before the full vesting period you will still receive a proportion.
Always check your Summary Plan Description (SPD) to understand how your employer’s retirement plan works.
A Note on Early Withdrawals and Penalties
You will be charged a 10% early withdrawal fee by IRS, if you make any withdrawals before the age of 59½. This will be in addition to you paying income tax. This means your $10,000 withdrawal by someone in the 25% federal tax bracket with 5% state tax; the actual take-home amount may be less than $6,000. Use our calculator to see what this will actually cost you
There are certain conditions which qualify for an exception. These include:
- Total and permanent disability,
- substantially equal periodic payments (SEPP/72t),
- separation from service aged 55 or over,
- qualified domestic relations order and
Levies from the IRS.