Roth vs. Traditional: How Equity Compensation Changes the Calculus

The Standard Advice Is Too Simplistic

You have heard the conventional wisdom: contribute to a Roth if you expect your tax rate to be higher in retirement, and choose traditional pretax contributions if you expect it to be lower. For someone earning a stable salary with predictable raises, this framework works reasonably well. For a tech employee whose W2 income swings by $200,000 or more from year to year because of RSU vesting schedules, option exercises, and ESPP dispositions, it is dangerously oversimplified.

The real question is not "will my tax rate be higher or lower in retirement?" The real question is "what is my marginal tax rate this year versus the effective rate I will pay on withdrawals in retirement?" When equity compensation creates dramatic income volatility, the answer changes from year to year, and so should your strategy.

Why Equity Compensation Creates Income Volatility

A typical tech compensation package creates income spikes that most financial planning advice fails to account for. Consider the common scenarios:

• RSU vesting cliffs: Your first anniversary vest drops $75,000 to $150,000 of ordinary income into a single quarter. Subsequent quarterly vests add $20,000 to $50,000 each.
• Option exercises: Exercising NSOs triggers ordinary income on the entire spread. Exercising ISOs triggers AMT preference items that can push you into AMT territory.
• ESPP sales: Disqualifying dispositions create ordinary income; qualifying dispositions split between ordinary income and capital gains.
• Job transitions: When you leave one company and join another, you may have accelerated vesting, a gap with no equity income, or overlapping vests from two employers.

This volatility means your marginal federal tax rate might be 24% one year, 35% the next, and 32% the year after. Each of those years calls for a different 401(k) strategy.

The Case for Pretax Contributions in High Income Years

When a large RSU vest pushes your adjusted gross income above $609,350 (single) or $731,200 (married filing jointly) in 2026, you are in the 37% federal bracket. Every dollar of pretax 401(k) contribution saves you 37 cents in federal tax, plus your applicable state tax rate.

This is the strongest possible case for traditional pretax contributions. You are buying a tax deduction at the highest retail price the tax code offers. If you withdraw that money in retirement at a lower rate, you pocket the difference permanently.

The math is unambiguous in these years. A $23,500 pretax contribution (the 2026 elective deferral limit) at the 37% marginal rate saves you $8,695 in federal tax. If you are in California, add another $2,585 at the 11% rate. Total first year tax savings: $11,280.

Compare that to a Roth contribution of the same $23,500, which provides zero current tax benefit. You pay $11,280 more in taxes this year for the promise of tax free withdrawals later. That promise only pays off if your retirement withdrawal rate exceeds 37%, which is unlikely for most retirees.

The Case for Roth in Lower Income Years

Not every year is a high income year, even for well compensated tech employees. Several common scenarios create windows where your marginal rate drops significantly:

• Early career: Before equity grants vest, you may earn $120,000 to $180,000 in base salary, placing you in the 22% or 24% bracket
• Startup years: You took an equity heavy offer with a $140,000 base salary and options that have not vested or are underwater
• Between jobs: A gap of two to six months between employers can reduce your annual income by $50,000 to $150,000
• Sabbaticals or leaves: Extended time off drops your W2 income for the year
• Post IPO adjustment: You left a company and your new employer's RSUs have not started vesting yet

In these years, your marginal rate may sit at 22% or 24%. Contributing to a Roth locks in tax free growth at a bargain rate. You pay 22 cents on the dollar now instead of potentially 32 or 35 cents later.

A Concrete Scenario: The $500K Engineer

Let us walk through the numbers for a senior engineer earning $300,000 in base salary with $200,000 in annual RSU vests.

High income year (full RSU vesting):

Now fast forward to retirement. If this engineer withdraws from the pretax account at an effective federal rate of 24% (a reasonable assumption for a retiree drawing $150,000 to $200,000 per year), the tax on the $23,500 withdrawal is $5,640. That means the pretax contribution saved a net $3,055 in federal tax per year of contribution ($8,695 saved now minus $5,640 paid later). Over a 20 year career of high income contributions, that is over $60,000 in federal tax savings alone, before accounting for the time value of deferral.

Low income year (between jobs, only $180,000 earned):

In this year, the engineer sits in the 24% bracket. A Roth contribution costs just $5,640 in federal tax on $23,500. That money will never be taxed again. If that same $23,500 were contributed pretax and later withdrawn at 24%, the net benefit is zero. But if the retirement rate turns out to be higher due to required minimum distributions, Social Security, or pension income, the Roth contribution wins outright.

The Fill the Bracket Strategy

The most sophisticated approach is not choosing one or the other. It is using pretax contributions to fill down to a specific bracket threshold, then directing additional savings to Roth accounts.

Here is how it works in practice:

1. Calculate your projected AGI for the year, including all expected RSU vests, option exercises, bonuses, and other income
2. Identify the nearest bracket boundary below your income. For 2026, the key thresholds are $197,300 (32% bracket starts, single) and $250,525 (35% bracket starts, single)
3. Use pretax contributions to bring your AGI down to that boundary. If your AGI is $520,000 and the 35% bracket starts at $250,525, pretax contributions alone will not bridge that gap. But they shave $23,500 off the top, saving at the 37% rate.
4. Direct any remaining savings capacity to Roth. Mega Backdoor Roth contributions (if your plan allows after tax contributions with in plan Roth conversions), Roth IRA via the backdoor method, and HSA contributions all provide additional tax diversified savings.

This approach is especially powerful for married couples where one spouse has stable income and the other has volatile equity compensation. The stable income sets a predictable floor, and the equity income determines whether the marginal savings go pretax or Roth.

Option Exercises Create Roth Conversion Windows

One of the most overlooked opportunities in equity compensation planning is the Roth conversion window that opens during job transitions.

The scenario: you leave a company in March. Your new employer's RSUs will not begin vesting until the following March. Your income for the transition year might be $150,000 to $200,000, roughly half your normal compensation. This is a rare year where your marginal rate drops to 24% or even 22%.

During this window:

• Convert traditional IRA or old 401(k) balances to Roth up to a target bracket threshold. If you earn $180,000 and want to stay in the 24% bracket (which runs up to $197,300 for single filers in 2026), you can convert approximately $17,300 at the 24% rate.
• Stack the conversion with your lower income year to fill brackets that would otherwise be "wasted" at a low rate.
• Avoid converting so much that you push into a higher bracket than your typical high income years. Converting at 35% defeats the purpose.

The same window appears when ISO holders exercise options and hold through a calendar year with reduced other income. If the AMT calculation yields a lower effective rate than your typical ordinary income rate, the after tax cost of the exercise creates a similar arbitrage opportunity.

The Decision Framework

Use this framework to decide your contribution type each year:

Choose pretax when:

• Your marginal federal rate is 35% or 37%
• You have a large RSU vest or option exercise pushing income well above $250,000
• You are in a high tax state (California, New York, New Jersey) and the state deduction amplifies the benefit
• You are confident your retirement withdrawal rate will be lower than your current marginal rate

Choose Roth when:

• Your marginal federal rate is 24% or below
• You are in a transition year between jobs with reduced equity income
• You are early in your career before significant equity grants vest
• You want to build a pool of tax free retirement assets that are not subject to required minimum distributions
• You expect future tax rates to increase due to legislation

Split your contributions when:

• Your income puts you near a bracket boundary and pretax contributions can push you into a lower bracket for part of your income
• You want tax diversification and your rate is in the 32% middle ground where the Roth vs. pretax comparison is genuinely uncertain
• Your plan allows mid year election changes and you can adjust based on actual vesting amounts

Revisit annually. The single biggest mistake tech employees make with retirement contributions is setting a Roth or pretax election once and forgetting it. When your income swings by six figures from year to year, last year's optimal strategy may be this year's worst choice. Review your election every January and again at midyear when you have better visibility into actual RSU vest values and total compensation.