The Ultimate Guide to 401(k) and IRA

What Are 401(k)s and IRAs?

401(k)s and IRAs are the two primary tax-advantaged retirement account types in the United States, and for most people, they're the foundation of retirement saving. Both offer tax benefits that significantly enhance long-term growth compared to taxable accounts, but they differ in important ways: who offers them, their contribution limits, their investment choices, and their rules.

A 401(k) is an employer-sponsored retirement plan: your employer sets it up, you contribute through payroll (often with a match), and you choose from a menu of investments the plan offers. A 401(k) is tied to your job, though you can roll it over when you leave.

An IRA (Individual Retirement Account) is an account you open yourself at a brokerage, with full control over investments and no employer involvement. Anyone with earned income can open and contribute to an IRA, regardless of employer benefits.

Both come in traditional (pre-tax contributions, tax-deferred growth, taxable withdrawals) and Roth (after-tax contributions, tax-free growth, tax-free qualified withdrawals) versions, with different rules and income limits. Understanding the differences and using both strategically maximizes your tax-advantaged retirement saving. This guide covers each account, the Roth vs traditional decision, contribution limits, and the optimal funding order.

The 401(k): Employer-Sponsored

A 401(k) is offered through your employer and funded through payroll deductions. Its key features:

Pre-tax contributions. Traditional 401(k) contributions are made pre-tax, reducing your current taxable income. If you earn $80,000 and contribute $10,000, your taxable income becomes $70,000 — you save tax now on the $10,000. The money grows tax-deferred, and withdrawals in retirement are taxed as ordinary income.

The employer match. The most valuable feature: many employers match a portion of your contributions, often 50% to 100% of your contributions up to a percentage of your salary (e.g., 50% match up to 6% of salary). A 50% match is a 50% return on your matched contributions — free money you should always capture. Failing to capture the full match is leaving compensation on the table. See our 401(k) guide.

High contribution limits. 401(k)s allow far higher contributions than IRAs — for 2024, $23,000 per year (plus a $7,500 catch-up at 50+), with total contributions (yours + employer) capped at $69,000. This lets you shelter far more than an IRA.

Limited investment choices. You choose from a menu your employer selects — typically a range of mutual funds, sometimes including target-date funds and index funds. The quality varies; some plans have excellent low-cost options, others have expensive funds. You can't invest in individual stocks or ETFs outside the menu (unlike an IRA).

Loan and hardship provisions. Some plans allow loans (borrowing from your balance, which must be repaid) or hardship withdrawals, but these should be last resorts — they reduce your compounding and can trigger taxes and penalties if not repaid.

Roth 401(k) option. Many employers offer a Roth 401(k) option: after-tax contributions, tax-free growth, tax-free qualified withdrawals. Unlike a Roth IRA, the Roth 401(k) has no income limits and shares the high 401(k) contribution limit. This is valuable for high earners who can't contribute to a Roth IRA directly.

Vesting. Employer match contributions may "vest" over time (you earn ownership over a period of years). Your own contributions are always yours immediately. Understand your plan's vesting schedule, especially if you might change jobs.

Roth 401(k) vs traditional 401(k). Choose Roth if you expect a higher tax bracket in retirement (pay tax now at a lower rate); choose traditional if you expect a lower bracket in retirement (deduct now at a higher rate). For young savers likely in their lowest bracket, Roth is often advantageous; for high earners in their peak bracket, traditional often wins. See our 401(k) calculator to model both.

The IRA: Individual Retirement Account

An IRA is an account you open yourself at a brokerage, with full control over investments. Its key features:

You choose the investments. Unlike a 401(k)'s limited menu, an IRA lets you invest in virtually any stock, ETF, mutual fund, or bond the brokerage offers. This means access to the lowest-cost, broadest index funds — a significant advantage over many 401(k) plans.

Lower contribution limits. For 2024, IRA contributions are capped at $7,000 per year ($8,000 at 50+), far lower than 401(k) limits. This is why IRAs supplement rather than replace 401(k)s for most savers.

Traditional IRA. Contributions may be tax-deductible (reducing current taxable income), growth is tax-deferred, and withdrawals are taxed as ordinary income. The deductibility phases out at higher incomes if you (or your spouse) have a workplace retirement plan — above certain income limits, you get no deduction, making a Roth IRA preferable. See our traditional IRA guide.

Roth IRA. Contributions are after-tax (no deduction), growth is tax-free, and qualified withdrawals are tax-free. The Roth is especially valuable for young savers in low brackets and for anyone who wants tax-free income in retirement. Income limits restrict direct Roth contributions at higher incomes, but backdoor Roth strategies (contributing to a traditional IRA and converting to Roth) can circumvent the limits. See our Roth IRA guide.

No employer involvement. You open and manage the IRA yourself, at any brokerage. It's portable and independent of your job.

More flexibility (and rules). IRAs have more flexibility in investments but also more rules — early withdrawal penalties (with exceptions for first home, education, and others), required minimum distributions for traditional IRAs (Roth IRAs have no RMDs during the owner's lifetime), and contribution eligibility rules.

Roth vs Traditional

The choice between Roth and traditional accounts is one of the most important retirement decisions, and it comes down to one question: do you expect your tax rate in retirement to be higher or lower than your current rate?

Traditional (pre-tax): you deduct contributions now (saving tax at your current rate) and pay tax on withdrawals in retirement (at your future rate). Best if you expect a lower tax bracket in retirement — you save tax at a high rate now and pay at a low rate later. This often suits high earners in their peak bracket.

Roth (after-tax): you pay tax on contributions now (at your current rate) and withdraw tax-free in retirement. Best if you expect a higher tax bracket in retirement — you pay tax at a low rate now and withdraw tax-free later. This often suits young savers in their lowest bracket and anyone who expects significant retirement income or rising tax rates.

Factors to consider:

• Current vs future income: if you're early in your career and expect higher income later, Roth is often better. If you're in your peak earning years, traditional often wins.
• Tax diversification: holding both Roth and traditional accounts gives you flexibility to manage your tax bill in retirement — withdraw from traditional to fill lower brackets, from Roth to avoid pushing into higher brackets.
• Roth IRAs have no RMDs: you're never forced to withdraw, making them excellent for legacy planning and tax-efficient growth in late retirement.
• Uncertainty about future tax rates: if you're unsure, tax diversification (some of each) hedges against changes in tax law.

A practical approach: for most young savers, prioritize Roth (especially Roth IRA) while in a low bracket; for high earners in their peak bracket, prioritize traditional 401(k) deductions. Many investors end up with both, providing tax diversification. Use our Roth IRA calculator and traditional IRA calculator to model both.

Contribution Limits

Contribution limits adjust annually for inflation. For 2024 (illustrative):

401(k):

• Employee contribution: $23,000/year.
• Catch-up (50+): additional $7,500.
• Total (employee + employer): $69,000 ($76,500 with catch-up).

IRA:

• Contribution: $7,000/year.
• Catch-up (50+): additional $1,000.

HSA (if eligible with a high-deductible health plan):

• Individual: $4,150/year; family: $8,300; catch-up (55+): $1,000.

Income limits: Roth IRA contributions phase out at higher incomes (around $146,000 single, $230,000 married for 2024). Traditional IRA deductibility phases out if you (or your spouse) have a workplace plan. 401(k)s and Roth 401(k)s have no income limits.

Maximizing contributions: for most savers, the goal is to contribute as much as possible across these accounts, in the optimal order (below). Even if you can't max everything, increasing contributions annually — especially with raises — compounds dramatically. Use our retirement savings calculator to see the impact.

The Optimal Funding Order

For most people, the optimal order to fund retirement accounts maximizes tax benefits and free money:

1. 401(k) to the full employer match. Always first — it's a 50–100% return on matched contributions. Never leave free money on the table.

2. Max a Roth IRA (or traditional IRA if you can deduct and prefer pre-tax). The Roth's tax-free growth is enormously valuable, especially for young savers. Full control over investments and no RMDs (for Roth) are bonuses.

3. Increase 401(k) contributions toward the annual limit. After the match and IRA, shelter more pre-tax in the 401(k) up to the $23,000 limit.

4. Max an HSA (if eligible with a high-deductible health plan). The triple tax advantage makes it the most tax-advantaged account available — a "stealth retirement account" for future medical costs.

5. Taxable brokerage. After maxing tax-advantaged accounts, invest surplus in a taxable account for flexibility (no withdrawal restrictions — valuable for early retirement).

Adjustments: high earners who can't contribute to a Roth IRA directly should use backdoor Roth contributions (contribute to a traditional IRA and convert to Roth). Those in their peak bracket may prefer more traditional 401(k) over Roth. Those aiming to retire before 59½ should build a taxable bridge to cover years before penalty-free retirement account withdrawals.

The exact order can vary by situation, but the principle is consistent: capture free money first, then maximize tax-advantaged growth, then build taxable flexibility. Use our 401(k) calculator, Roth IRA calculator, and retirement savings calculator to model your contributions.

For official guidance, the IRS provides detailed, up-to-date information.

You can verify current figures directly with the IRS.

The Bottom Line

401(k)s and IRAs are the two pillars of retirement saving, and using both strategically maximizes your tax-advantaged growth. Capture the 401(k) match first (free money), then max a Roth IRA (tax-free growth, especially valuable for young savers), then increase 401(k) contributions toward the limit, then max an HSA if eligible, then build a taxable account for flexibility. Choose Roth or traditional based on whether you expect a higher or lower tax bracket in retirement — and consider holding both for tax diversification. The combination of these accounts, funded consistently over decades, is how most Americans build a secure retirement. Use our calculators to model your contributions, and see our retirement planning guide and 401(k) guide for the full framework.