Traditional vs Roth 401(k)

A 401(k) is an employer-sponsored retirement plan that allows employees to contribute up to $24,000 in 2026 ($32,000 if age 50+). The key decision is whether those contributions go to a Traditional or Roth bucket—or both. In 2026, fewer than 30% of plans offer Roth 401(k) deferrals, but that's changing rapidly. If your employer doesn't offer Roth, consider a Backdoor Roth IRA strategy instead.

Your employer may match contributions (average 3-4% of salary). Match funds are always deposited to the Traditional side, even if you elect Roth deferrals. This is an important distinction for Roth ladder planning.

Traditional 401(k) contributions reduce your taxable income dollar-for-dollar in the year contributed. If you earn $150,000 and contribute $24,000, you report only $126,000 of taxable income. This immediate tax deduction is powerful if you're in the 32% or 35% federal tax bracket.

However, Traditional 401(k) distributions are taxed as ordinary income in retirement. Required Minimum Distributions (RMDs) start at age 73 under the SECURE Act 2.0. In 2026, the RMD divisor for age 73 is 14.8, meaning you'll withdraw roughly 6.75% of your balance annually—even if you don't need the money.

Roth 401(k) contributions are made with after-tax dollars—no immediate income tax reduction. But all growth is tax-free, and qualified withdrawals (age 59.5+, 5-year hold) are never taxed. This is the opposite benefit: pay tax now, zero tax later.

The power of Roth 401(k) is compounding tax-free growth. A 40-year-old contributing $24,000 annually for 25 years (age 65 retirement) grows to approximately $1.2M (assuming 6% annual returns). All of that growth—roughly $600k—is tax-free if the withdrawal is qualified.

Many plans (especially larger employer 401(k)s) now allow in-plan Roth conversions. This means you can convert your existing Traditional 401(k) balance—or future contributions—to Roth without leaving the plan or rolling to an IRA. The conversion is taxable in the year of conversion, but the balance is now Roth.

Unlike standalone Roth IRA conversions, in-plan conversions are not subject to the pro-rata rule—IF the plan properly segregates the converted funds from other Traditional balances. Always verify your plan administrator has this capability before planning a large conversion.

The "Mega Backdoor Roth" is the most powerful strategy for high earners. While everyone can contribute $24,000 to a 401(k), plans can allow contributions up to the annual limit of $69,000 (2026). Your employer match uses some of this room, but after-tax contributions fill the gap.

Physicians, dentists, and solo business owners love Mega Backdoor Roth because they can contribute $24,000 + $46,500 = $70,500 to tax-advantaged accounts (before Solo 401(k) self-employed contributions). That's $70.5k growing tax-free per year, compounding for 25 years to roughly $3.5M.

Not all plans allow Mega Backdoor conversions. Check your plan summary to confirm the plan permits (1) after-tax contributions, (2) in-plan Roth conversions, and (3) timely conversions (same pay period or month is ideal to minimize earnings).

The core question: Are you in a higher tax bracket now or in retirement? 2026 federal tax brackets range from 10% to 37%. If you're single earning $200k (24% bracket) and expect to withdraw only $80k in retirement (12% bracket), Traditional contributions now save you 12% upfront.

Consider state income tax too. If you work in New York (8.82% top rate) and plan to retire in Florida (0% income tax), Traditional contributions are more valuable than the federal analysis suggests. A 32% federal + 8.82% state = 40.82% tax rate spread creates huge Roth advantage.

The Roth ladder (also called "Roth conversion ladder") is a strategy to access Roth funds before age 59.5 without penalty. Here's how it works: Year 1, convert $100k Traditional IRA to Roth, pay the tax. Wait 5 years. In year 6, withdraw the $100k contribution (contributions are always accessible tax-free). Meanwhile, the conversion earnings grow tax-free inside the Roth.

This strategy works best if you have a clear spending plan and convert during low-income years (sabbatical, business downturn). Each conversion is taxable in the year it occurs, so space conversions across multiple years to stay in lower brackets. A $1M conversion in one year might trigger 35-37% tax. Spread over 5 years at $200k each, you might pay 22-24% tax per year.