This is a tax-timing decision—not a contest between two account labels

Lesson 22 audited the employer plan. Lesson 23 focuses on one of the most consequential choices inside that plan: whether employee contributions receive Traditional pre-tax treatment, designated Roth treatment, or some combination when the plan permits both.

The wrong question is “Which one is always better?” The stronger question is: What tax rate am I avoiding today, what future tax rates are plausible, what does each choice do to my current cash flow, and how much flexibility do I want later?

Traditional vs. Roth is primarily a tax-timing decision: Traditional generally postpones income tax, while Roth generally pays tax now in exchange for qualified tax-free withdrawals later.

Traditional and Roth change when income tax is paid

Salary deferrals generally remain subject to Social Security and Medicare taxes even when they receive pre-tax income-tax treatment. Traditional is therefore not simply “tax-free today.”

Equal contribution dollars are not equal paycheck cost

Suppose the participant can contribute $10,000 and the simplified current federal marginal income-tax rate is 24%.

	Contribution invested	Simplified current federal income-tax effect
Traditional	$10,000	About $2,400 of current federal income tax deferred
Roth	$10,000	About $2,400 more current federal income tax compared with the simplified pre-tax case

The two accounts receive the same nominal contribution, but the Roth contribution generally requires more current after-tax cash. That means an equal-dollar comparison can quietly give Roth more economic resources.

Compare Traditional and Roth at equal cash-flow cost—not only equal contribution dollars—because a Roth contribution usually costs more current take-home pay than the same nominal pre-tax contribution.

Equal cash-flow cost produces a cleaner comparison

Assume an investor can give up approximately $7,600 of current take-home pay and uses a simplified 24% marginal federal income-tax rate.

Use scenarios instead of pretending to know your future tax rate

Now apply a purely hypothetical 3× growth multiple to the equal-cash-flow example. This is not a return forecast.

Traditional: $10,000 → $30,000.

Roth: $7,600 → $22,800.

Hypothetical future tax rate on Traditional withdrawal	Traditional after-tax value	Qualified Roth value
12%	$26,400	$22,800
24%	$22,800	$22,800
32%	$20,400	$22,800

Under these simplified assumptions, the result changes when the tax rate eventually paid on Traditional withdrawals changes. The lesson is not that 24% is a universal cutoff. The lesson is that the tax rate avoided today versus the tax rate paid later is a major driver of the comparison.

Current marginal rate is usually the better starting point

A participant may say, “My average tax rate is 14%.” That number can be useful for other purposes, but it does not necessarily measure the tax value of the next dollar of a Traditional contribution.

For a simplified Traditional-versus-Roth decision, the marginal income-tax rate on the affected dollars is usually the more relevant starting point. The real calculation can become more complex when contributions cross tax brackets or interact with deductions, credits, filing status, or state taxes.

Future tax exposure comes from more than tax-law changes

Your retirement tax rate may differ because of:

• pension income,
• Social Security,
• Traditional retirement withdrawals,
• required distributions,
• part-time or consulting income,
• investment income,
• filing status,
• deductions,
• state residence,
• and future tax-law changes.

That is why this lesson uses a lower-rate, similar-rate, and higher-rate scenario rather than pretending one retirement tax rate can be predicted decades in advance.

Traditional and Roth can be used together

If a workplace plan offers both tax treatments, a participant can generally split elective contributions between Traditional and designated Roth in an allowed proportion.

For example, a $20,000 employee deferral might be:

• $20,000 Traditional / $0 Roth,
• $10,000 Traditional / $10,000 Roth,
• $0 Traditional / $20,000 Roth,
• or another split allowed by the plan.

What it does not mean is a full employee-deferral limit for Traditional plus another full employee-deferral limit for Roth.

Traditional and Roth contributions share the workplace-plan deferral limit, but holding both tax treatments can give a retiree more flexibility over which type of money to withdraw later.

Tax diversification is flexibility—not a universal 50/50 rule

Holding both Traditional and Roth money can give a retiree more options when deciding which account to draw from in a particular year. For example, the tax impact of an additional Traditional withdrawal can differ from using qualified Roth money.

That flexibility can be valuable, but it does not prove that every participant should use a 50/50 split. Current tax rate, cash-flow capacity, future taxable income, plan features, existing balances, state taxes, and retirement strategy still matter.

A workplace Roth does not use the Roth IRA income-eligibility test

Designated Roth contributions inside a workplace plan do not use the same income eligibility limits that apply to Roth IRA contributions. A participant can therefore have access to a Roth 401(k) or Roth 403(b) even when income would restrict a direct Roth IRA contribution.

Lesson 24 will cover IRA eligibility and contribution rules separately.

Qualified workplace Roth withdrawals require more than reaching age 59½

A qualified distribution from a designated Roth workplace account generally requires both:

• completion of the applicable five-taxable-year participation period, and
• a qualifying event such as reaching age 59½, death, or disability.

Someone who begins designated Roth contributions late in a career should therefore not assume that age alone automatically makes every Roth workplace distribution qualified.

Nonqualified workplace Roth distributions follow different mechanics from Roth IRAs

For a nonqualified distribution from a designated Roth workplace account, current IRS rules generally allocate the payment proportionally between contributions and earnings. The earnings portion can be taxable, and additional early-distribution rules may also apply depending on the facts.

This is one reason not to assume that all “Roth” accounts share the same withdrawal-order rules. Roth IRA distribution ordering will be addressed in Lesson 24.

Workplace Roth balances now have different owner-lifetime RMD treatment

Under current federal rules, designated Roth balances in 401(k) and 403(b) plans are not subject to required minimum distributions during the original owner’s lifetime. Traditional workplace balances generally remain subject to RMD rules, although certain current-employer plan participants may qualify for a delayed required-beginning date under applicable rules.

This difference can affect later-life withdrawal flexibility, but it is only one factor in the Traditional-versus-Roth decision.

Employer contributions can have plan-specific Roth treatment

It is outdated to assume that every employer match associated with a Roth employee contribution must always remain pre-tax. SECURE 2.0 allows plans to offer Roth treatment for certain fully vested employer matching or nonelective contributions if the plan adopts that feature and the legal requirements are satisfied.

The participant therefore needs to inspect the actual plan:

• Does the employer match Roth employee contributions?
• Where does the employer contribution land?
• Does the plan allow eligible employer contributions to be designated Roth?
• If so, when is that contribution included in taxable income?

2026 catch-up rules can make part of the Roth decision mandatory

Lesson 22 introduced the 2026 Roth catch-up rule. Under current rules, certain participants whose prior-year wages from the sponsoring employer exceeded the applicable $150,000 threshold generally must make eligible catch-up contributions on a Roth basis, subject to the detailed statutory and plan rules.

That means a higher-earning catch-up participant may not have complete freedom to choose pre-tax treatment for every catch-up dollar.

Do not use “young = Roth, older = Traditional” as the rule

Age can affect the decision indirectly, but it is not enough by itself. Two people the same age can have completely different tax-timing decisions because of current income, expected earnings growth, pension income, existing Traditional balances, existing Roth balances, state taxes, contribution capacity, and retirement timing.

Interactive practice · Traditional vs. Roth Tax-Timing Lab

Compare equal contribution dollars and equal current cash-flow cost

This simplified educational model does not calculate an individual tax return, credits, deductions, Social Security or Medicare taxes, state-specific rules, future law changes, penalties, or plan eligibility. It does not recommend Traditional or Roth.

Comparison modeEqual contribution dollarsEqual current cash-flow cost Contribution / take-home sacrifice ($) Current marginal federal rate % Optional state income-tax rate % Hypothetical growth multiple Future tax rate — lower % Future tax rate — similar % Future tax rate — higher % Existing Traditional balance ($) Existing Roth balance ($) Years since first designated Roth contribution to this plan Participant age

Compare tax timing

Apply this lesson · Intermediate

Compare the tax timing—not just the account labels

Answer all four questions correctly to pass.

1. Which comparison is stronger when evaluating Traditional versus Roth?

Compare only equal nominal contribution amounts.Also compare the current after-tax cash-flow cost because the same Roth contribution usually costs more take-home pay.

2. Can an employee generally contribute the full workplace elective-deferral limit to Traditional and another full limit to Roth in the same plan year?

Yes, the limits are separate.No. Traditional and designated Roth elective contributions share the applicable employee-deferral limit.

3. A participant is age 62 but first contributed to the plan’s designated Roth account two tax years ago. Are distributions automatically qualified solely because the participant is over age 59½?

Yes.No. The five-taxable-year requirement also generally matters.

4. Which statement reflects stronger decision-making?

I’m young, so Roth is automatically best.I should compare current marginal tax cost, several future tax-rate scenarios, cash-flow capacity, existing tax balances, and plan rules.

Check my answersTry again

Quick knowledge check

1. Why can equal Traditional and Roth contribution amounts produce unequal current cash-flow cost?
2. Why is marginal tax rate generally a better starting point than average tax rate for this decision?
3. What two broad requirements generally make a designated Roth workplace distribution qualified?
4. Why can holding both Traditional and Roth money create retirement tax flexibility without proving a 50/50 split is best?

Show answers

1. Roth contributions are made with after-tax dollars, while Traditional contributions generally defer current income tax. 2. The contribution affects the next dollars of taxable income rather than the average tax rate across all income, although bracket interactions can complicate the result. 3. The applicable five-taxable-year participation period plus a qualifying event such as age 59½, death, or disability. 4. Multiple tax treatments can create withdrawal choices later, but the appropriate split depends on current tax cost, future income scenarios, balances, cash flow, and plan rules.

Reliable further reading

• IRS: Designated Roth Account FAQs — contribution treatment, qualified distributions, five-year rules, and Roth workplace mechanics.
• IRS Topic No. 424: 401(k) Plans — pre-tax deferrals and payroll-tax treatment.
• IRS: Catch-Up Contributions — current catch-up rules, including the 2026 Roth catch-up requirement for certain participants.
• IRS: Required Minimum Distribution FAQs — current RMD treatment for workplace retirement accounts.
• IRS Notice 2024-2 — SECURE 2.0 guidance including designated Roth employer contribution provisions.

Sources reviewed: October 21, 2026

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Finlitera provides general financial education, not individualized tax, investment, legal, or retirement advice. Tax rates, plan rules, RMD rules, catch-up requirements, state taxes, qualified-distribution rules, and employer contribution options can change. Your actual plan documents, tax return, and current official guidance control.