The two accounts differ on one question: do you want the tax bill now or later? Plus the Roth feature almost nobody knows about.
An IRA is the account you open yourself
A 401(k) belongs to your employer's plan. An Individual Retirement Arrangement is yours: you open it at any brokerage, choose your own investments, and it follows you between jobs because it was never tied to one.
That difference matters more than people realise. Employer plans offer a fixed menu of funds, sometimes an expensive one. In an IRA you can hold the same broad index funds at the lowest cost available anywhere — which is why "get the match, then fund an IRA" is such common guidance.
The whole question is when you pay tax
Traditional: you may deduct the contribution now, the money grows untaxed, and every dollar you withdraw in retirement is taxed as ordinary income.
Roth: you contribute money you have already paid tax on, it grows untaxed, and qualified withdrawals — contributions and all the growth — come out tax-free.
If tax rates and your bracket never changed, the two would produce identical results. They differ because your bracket changes, and because tax law does.
The rule of thumb, and its limits
- Expect a higher bracket later? Roth. Pay tax now at your low rate.
- Expect a lower bracket later? Traditional. Take the deduction at your high rate.
In practice that points young people, students and anyone early in a career towards Roth, and points people at peak earnings towards traditional. But nobody knows their future bracket, and nobody knows what Congress will do to rates in thirty years. Holding some of each is a legitimate answer rather than a failure to decide — it gives you a choice of which account to draw from later.
Roth's underrated feature
You can withdraw your Roth contributions — not the earnings — at any time, for any reason, with no tax and no penalty. You already paid the tax on that money.
This makes a Roth IRA a far more flexible place for long-term savings than most people assume, and it removes the main objection to funding one early: that the money is locked away for forty years. It is not. The earnings are.
That said, money you take out cannot be put back beyond the annual limit, and every dollar removed stops compounding. Treat it as an emergency exit, not a plan.
The IRS caps annual IRA contributions, allows extra for people over 50, and phases out Roth eligibility above certain incomes — with the deduction for traditional contributions phasing out too if you are covered by a workplace plan. All of these figures move most years, so we deliberately do not print them. Check irs.gov for the current numbers. One deadline worth knowing regardless: you generally have until the tax filing deadline the following spring to make a contribution for the prior year.
Common mistakes
- Contributing and stopping there. Money in an IRA sits as cash until you invest it. A distressing number of accounts have sat uninvested for years.
- Assuming you earn too much for a Roth. Income limits apply to direct contributions. There is a legal workaround commonly called a backdoor Roth, which is straightforward for some people and messy for others depending on existing traditional balances — worth asking a tax professional about rather than improvising.
- Choosing the account and ignoring the fund. Roth versus traditional is a tax decision. What you buy inside is the investment decision, and over decades the second one usually matters more.
- Waiting for certainty. The difference between the two accounts is smaller than the difference between starting now and starting in five years.
Where the IRA fits
The usual order: capture your full employer match first, then fund an IRA where you control the costs, then return to the 401(k) for more. Inside either, the answer to what to buy is generally a broad, low-cost index fund.
This is educational content, not personalised tax or investment advice. Contribution eligibility depends on your income, filing status and workplace coverage — confirm yours before contributing.