Retirement Accounts Explained: 401(k), IRA and Roth

Retirement accounts confuse people because the names describe tax law rather than anything intuitive. "401(k)" is a section of the tax code. "IRA" is an acronym for a description.

Underneath, there are only a few ideas, and they are all understandable in an afternoon.

An account is a container, not an investment

This is the single most important sentence in the topic.

A 401(k) or an IRA is a container with special tax rules. What goes inside it — funds, stocks, bonds, cash — is a separate decision. Two people can hold identical accounts and end up with wildly different results based only on what they put in.

The most common expensive mistake in personal finance is contributing money to a retirement account and never actually investing it, leaving it sitting in cash for years while the contributor believes it is growing.

The one question: when do you pay the tax?

Every account type is a variation on that question.

Pre-tax gives you the break today. Roth gives it to you later. Which is better depends on whether your tax rate in retirement is higher or lower than it is now — something nobody can know with certainty, which is precisely why many people end up holding some of each.

Both give you the same powerful middle row: growth that is not taxed along the way.

The account types

401(k), 403(b), 457 — workplace plans. Contributions usually come straight from your paycheck, and the investment menu is chosen by the plan. Many offer both traditional and Roth versions.

Traditional IRA — an individual account you open yourself, with a much wider investment choice than most workplace plans. Whether contributions are deductible can depend on income and on whether a workplace plan covers you.

Roth IRA — the after-tax individual version. Eligibility to contribute directly phases out above certain income levels.

Rollovers — when leaving a job, a workplace plan can generally be moved into an IRA or a new employer's plan without triggering tax, if done correctly. Doing it incorrectly can be costly, so this is a step worth reading the IRS guidance on.

The employer match

If your employer matches contributions, that is part of your compensation. A common structure matches your contributions up to a percentage of salary.

Vesting decides when the employer's portion is fully yours — some plans grant it immediately, others over several years. Your own contributions are always yours.

Check your plan documents for the exact match formula and vesting schedule; both vary widely between employers.

Limits, penalties and required withdrawals

• Contribution limits are set annually by the IRS, with catch-up amounts above a certain age.
• Early withdrawals before the qualifying age generally trigger income tax plus a penalty, with specific exceptions.
• Required minimum distributions apply to certain account types once you reach a set age.

Every one of those thresholds has changed by legislation within recent memory, which is why this article deliberately quotes none of them. IRS.gov carries the current figures, and it is the only source worth trusting for them.

Why starting early matters more here than anywhere

Retirement accounts hold money for decades, which is the exact condition compounding needs.

Common mistakes

1. Contributing but not investing, leaving the balance in cash by default.
2. Not contributing enough to receive the full employer match.
3. Cashing out a plan when changing jobs, triggering tax and penalties and ending the compounding.
4. Ignoring the investment costs inside the plan, which compound against you the same way returns compound for you.
5. Waiting for a "real" salary to start. The first years contribute the most, because they have the most time.

Where to verify everything here

IRS.gov for limits, rules and withdrawal requirements. Investor.gov for understanding what you hold inside the account. Your plan documents for the match formula, vesting schedule and fee disclosures — the details that vary by employer and that no article can answer for you.