Tax treatment differs across account types, and the difference compounds over decades. Same dollars, same funds, different tax bill at both ends.
It's also easy to find confusing. The names are about as simple as the tax code that produced them. The 401(k), the 403(b), the 457, the IRA, the Roth IRA, the SEP-IRA, the SIMPLE IRA, the HSA. Each is named after the section of tax code that created it rather than what it actually does. It's like naming your dog after the aisle where you bought the leash.
The three categories, in plain terms
Tax-deferred (the traditional 401(k), the traditional IRA): you contribute pre-tax dollars that grow without annual taxation, and the money is taxed as ordinary income when you withdraw it in retirement.
Tax-free (the Roth 401(k), the Roth IRA): you contribute already-taxed dollars that grow tax-free, and qualified withdrawals in retirement are not taxed at all. The Roth IRA has direct income limits, so above a certain income you can't contribute to one directly. Part 3 below tells you where you sit and what to do about it. The Roth 401(k) has no income limit at all.
Taxable brokerage: no contribution limits, no withdrawal restrictions, no tax advantages. Gains on anything held less than a year are taxed at your ordinary income rate, gains on anything held more than a year at lower preferential rates, and dividends are taxed annually whether you sell or not.
Roth or pre-tax, and how to choose
Most plans now let you pick, and the step above never asks you which, because the honest answer is that it depends on something nobody knows. Pre-tax comes off this year's taxable income, so you pay less tax now and pay ordinary income tax on the whole balance when you take it out. Roth gets no deduction now, and qualified withdrawals come out untaxed. So the choice turns on one comparison: is the rate you'd pay on that money today higher or lower than the rate you'd pay on it when you spend it? If today's rate is higher, pre-tax wins. If the later rate is higher, Roth wins.
Nobody knows their rate in thirty years. Your income will move, and Congress rewrites the brackets. But there's a shape to the answer early on. In your twenties and thirties your income is usually the lowest it will ever be, which means the deduction you'd get from going pre-tax is worth the least it will ever be worth, and the tax you pay on a Roth contribution is the cheapest tax you'll ever pay on that money. That's the case for Roth early.
Three things push the other way. A high income now, in one of the upper brackets, makes the deduction worth a lot today. Living in a state with income tax now and planning to stop working somewhere without one does the same. And if your savings rate is so high that pre-tax is the only way you can afford to fill the account at all, filling it beats optimizing it. Plenty of people split the difference and put some in each, which is a defensible answer to a question that has no certain one. When the amounts get large, a CPA or a tax professional is worth the fee, because they can see your actual bracket and your state and we can't.
The HSA earns second position
As of this writing it's the only account type in the U.S. system with a triple tax advantage: contributions are deductible going in, growth is not taxed, and withdrawals for qualified medical expenses come out tax-free. No other account combines all three. It requires a qualifying high-deductible health plan, which not every employer offers. After age 65, withdrawals for non-medical expenses are taxed as ordinary income, the same as a traditional IRA, so any unspent balance keeps its value as retirement money. Treat the HSA as a stealth retirement account, not a medical savings account.
If your plan is a 403(b)
Teachers, nurses, professors and people who work for non-profits usually have a 403(b) instead of a 401(k). Treat it as the same container. Money comes out of your paycheck before tax, or after tax if your plan offers a Roth version, it can carry an employer match, and it shares one yearly employee contribution limit with the 401(k), because the same section of the tax code sets both. That's the figure in the table below. If you have a 403(b) and a 401(k) in the same year, that one limit covers the two of them together, not each of them separately (IRS, 403(b) contribution limits). The limit changes most years, so check the current one before you set your contribution.
One difference is worth your attention, and it's what's on the menu. A 403(b) can hold mutual funds or annuity contracts sold by an insurance company, and annuities are a far bigger share of these plans than of 401(k) plans. The ICI and ISS Market Intelligence report published in August 2025 put 32% of the assets in large ERISA 403(b) plans in fixed and variable annuities as of 2022, against 67% in mutual funds. The SEC's own page for teachers says fees vary product to product and come out of your returns every year, and that taking money out of an annuity in the first few years can trigger what's called a surrender charge, a fee for leaving early (SEC, Saving and Investing for Teachers). A product charging 1.5% a year and an index fund charging 0.05% can hold much the same stocks. Step nine prices what that gap does to your balance over a career. Ask your plan for its fee disclosure, find the cheapest broad index fund on the list, and if there's nothing cheap on the menu, take the match and put the next dollar into an IRA you open yourself.
If your eyes have rolled back in your head
We get it. Read this nonsense one more time. Let your brain process it. It's okay to think it's annoying. It is. It's alphabet soup that tastes like crap. But it is what it is, so learn it. Once you do, it's pretty easy to master, because there are only a few things worth knowing about each account. We know you can do this. You know you can do this. You don't have to be excited about it. You can still do it.