What the 401(k) Tax Break Is Actually Worth

"Contributions are pre-tax" is the entire pitch most people ever hear for a traditional 401(k). Here is what the phrase is actually worth in dollars — and the fine print that matters just as much.

The deferral, priced

A traditional contribution comes out of your pay before federal income tax is computed. Contribute $10,000 with a 24% marginal rate and your tax bill this year drops by about $2,400 — the paycheck shrinks by roughly $7,600, not $10,000. The state usually piles on: in a state with a 5% income tax, the same contribution costs closer to $7,100 of take-home pay. You are buying $10,000 of invested savings at a meaningful discount, priced at your marginal rate — the higher your bracket, the bigger the discount.

Growth without drag

Inside the account, dividends and sales generate no annual tax. A taxable brokerage account loses a slice of each year's dividends and every rebalancing gain to tax as it goes; the 401(k) compounds the gross amount for decades. This quiet feature is worth more over 30 years than most people guess — tax drag of even half a percent a year compounds into a five-figure difference on a six-figure balance.

The two caveats

• The tax is deferred, not forgiven. Withdrawals in retirement are ordinary income. The bet embedded in every traditional contribution is that your rate in retirement will be at or below your rate today — often true, since retirees fill the low brackets first with no wage income competing, but not guaranteed.
• FICA still applies. 401(k) contributions dodge income tax, not Social Security and Medicare tax. The 7.65% comes out regardless — which is also why your Social Security benefit record is unaffected by contributing.

Order of operations

None of the above outranks the employer match. Matched dollars are an instant, guaranteed return that no tax analysis touches — capture the full match before optimizing anything else. The employer match calculator shows what your formula leaves on the table, the take-home pay calculator shows what a contribution actually costs per check after the tax break, and the 401(k) calculator projects what the deferred, undragged compounding builds by retirement.

Run your own numbers

More on taxes

• Roth or Traditional: The One Question That Settles Most of It
• No, Your Bonus Is Not Taxed at a Higher Rate — It Just Looks That Way
• The HSA Triple Advantage: The Most Tax-Favored Account in the Code

This article is general education, not tax, legal, investment, or financial advice. Figures used in examples are illustrations, not quotes or predictions. For decisions that depend on your full situation, talk to a qualified professional.