Your 401(k) is also a tax instrument

Most people meet their 401(k) at a new-hire orientation, pick a number between six and ten, check the box marked "target-date fund," and never think about it again in any structural way. That is not a criticism. The system is designed to be ignorable. The problem is that the ignorable choice is rarely the right one, because a 401(k) is not really a retirement account. It is a tax instrument that happens to hold investments.

Consider the 2026 numbers. The base employee contribution limit is $23,500. Workers aged 50 and over add a $7,500 catch-up. Workers aged 60 to 63 — a new bracket added by SECURE 2.0 — can contribute a higher catch-up of $11,250. Employer contributions, including match, push the combined cap for the account to $70,000. A couple both over 60, both earning enough to max out, can move $93,500 of their own money out of this year's taxable income, before a dollar of match. For a household in the 24% federal bracket and 6.37% New Jersey, that's roughly $28,400 of tax not paid this year.

That is the first job the 401(k) does. The second job is quieter and arguably more important. It gives you a choice about when to pay the tax.

Most plans now offer both a pre-tax and a Roth option. Same account, same investments, different tax treatment. Pre-tax contributions reduce this year's income; Roth contributions don't, but every dollar you withdraw in retirement — including decades of growth — is tax-free. The default advice ("pre-tax if you expect lower taxes in retirement, Roth if higher") is correct at the level of a bumper sticker and unhelpful at the level of a real household, because almost no one actually knows what their tax bracket looks like in thirty years.

The way we usually think about it: in your highest earning years, pre-tax mostly wins. The dollar you don't pay in tax today compounds for decades before you ever see it again. In lower-income years — a sabbatical, a business ramp, a partner out of the workforce — Roth mostly wins, because you're paying tax at a rate you may never see again. The couple who moves a few years of their twenty-five-year career between the two baskets usually ends up with a more flexible retirement than the couple who picks one and holds.

Then there's the lever almost nobody uses: the mega-backdoor Roth. If your plan allows after-tax (non-Roth) contributions and in-plan conversions or in-service withdrawals — roughly 40% of large-employer plans do — you can push tens of thousands of additional dollars per year into Roth treatment without any income limit. For a high-earning engineer or executive whose regular Roth contribution is phased out by income, this is the single largest tax-advantaged savings opportunity in the code, and most of the plan documents explaining it are deliberately boring.

A 401(k) is also a coordination problem. We see plans with brilliant institutional share classes at three basis points that clients roll into a retail IRA at forty. We see clients who contribute up to the match and then stop — leaving the rest of the tax lever on the table — because no one ever told them the match is not the cap. We see people at 62 who didn't know their plan allowed in-service distributions, and so kept contributing to a vehicle they could have partially rolled into something cheaper years earlier.

The 401(k) is not a retirement account. It is a contract the IRS lets you sign with yourself, and the terms are better than almost anything else on offer. Read it like a contract.

A final note for business owners with employees: the employer-sponsored plan is also a recruiting and retention tool, and the design of that plan matters more than most owners realize. A SIMPLE IRA, a SEP, a safe-harbor 401(k), and a full 401(k) with profit-sharing are not interchangeable. They have different contribution limits, different administrative burdens, and different ways of benefiting the owner relative to the staff. A 48-year-old business owner who can put $70,000 into her own retirement account while satisfying a reasonable safe-harbor match for her six employees has a dramatically different tax picture than one using a SEP that limits contributions to 25% of W-2 compensation. The right plan structure is worth a conversation with someone who earns nothing from the plan itself.