As a couple deciding between Roth and traditional 401(k) contributions, how should they split contributions now based on current and expected future tax brackets?

The key question is not simply “Roth or traditional?” It is:

What marginal tax rate are you paying on the next dollar today, versus what tax rate do you realistically expect to pay on that dollar when you withdraw it? For a couple, I’d generally approach it this way.

1. Start with each spouse's marginal bracket

For 2026, married filing jointly has these federal marginal brackets: 22% begins at $100,800 of taxable income, 24% at $211,400, 32% at $403,550, 35% at $512,450, and 37% at $768,700. The standard deduction is $32,200.

So, for example:

• If you're in the 32% bracket today and expect to be around 22–24% in retirement, traditional 401(k) contributions are usually very attractive.
• If you're in the 22% bracket today but expect retirement income to put you in the 24–32% range, Roth becomes more compelling.
• If you're in the 12% bracket today, I'd generally lean heavily toward Roth unless you have a strong reason to expect substantially lower taxes later.

Remember that a traditional contribution saves tax at your marginal rate today, while retirement withdrawals are taxed progressively. Roth contributions are taxed today, but qualified withdrawals are generally tax-free.

2. Don't necessarily split the two spouses 50/50

This is one of the most useful ways to think about it.

Suppose:

• Spouse A earns $250k and is firmly in the 24% marginal bracket.
• Spouse B earns $70k and is in the 12% or 22% range.
• You expect both to have substantial retirement income.

I'd be inclined to have Spouse A favor traditional contributions because each traditional dollar is currently avoiding a relatively high marginal tax rate.

Meanwhile, Spouse B could favor Roth, particularly if their current marginal rate is low.

That gives the household a mixture of tax-deferred and tax-free assets without requiring each spouse to make the same choice.

3. Think of Roth as buying tax insurance

Even if traditional wins mathematically based on your expected brackets, having some Roth money can be valuable.

A retirement portfolio containing:

• traditional 401(k)s,
• Roth 401(k)s/Roth IRAs, and
• taxable investments

gives you flexibility to choose where retirement income comes from each year.

For example, if you have $100k of living expenses in retirement, you might take some taxable income from traditional accounts and then use Roth money for additional spending without increasing your taxable income.

That flexibility can be particularly valuable if one spouse dies, because the surviving spouse may eventually file as single and face different brackets.

4. A useful rule of thumb

I'd roughly categorize the decision like this:

These are rules of thumb rather than precise break-even calculations.

5. There's an important wrinkle: the contribution limits are shared by tax type, not by type separately

In 2026, each employee can make up to $24,500 of elective 401(k) deferrals, with traditional and Roth contributions combined. Someone eligible for catch-up contributions can contribute more.

So you could, for example, have:

• Spouse A: $20k traditional + $4.5k Roth
• Spouse B: $5k traditional + $19.5k Roth

rather than thinking each spouse has to choose 100% one way or the other.

And get the full employer match first, regardless of whether your own contributions are Roth or traditional—the match is generally a separate employer contribution.

6. The biggest factor people miss: retirement income

Don't compare your current salary with your expected retirement salary.

Compare:

Current marginal tax rate on the contribution

versus

marginal tax rate on the withdrawal

Your retirement taxable income could include:

• Social Security
• pensions
• traditional 401(k)s/IRAs
• rental/business income
• investment income
• required distributions
• a spouse's retirement income

If you have, say, $2–3 million of traditional retirement accounts, putting everything into traditional accounts today may create a surprisingly large future tax bill.

Conversely, if you'll have a modest traditional balance and mostly Social Security plus taxable/Roth assets, traditional contributions today can be extremely efficient.

My default for a two-income couple

Absent other information, I'd consider a barbell approach:

• Higher-income spouse: primarily traditional 401(k)
• Lower-income spouse: primarily Roth 401(k)
• Both: enough traditional to capture valuable deductions, enough Roth to build meaningful tax-free assets
• As retirement approaches: gradually evaluate whether additional Roth conversions make sense

The optimal split can be quite different depending on your actual numbers.

If you give me each spouse's age, salary, current 401(k)/IRA balances, approximate retirement age, expected Social Security/pension income, and whether you expect income to rise or fall, I can calculate a much more concrete e.g. “Spouse A 80% traditional / 20% Roth, Spouse B 30% traditional / 70% Roth” recommendation using the 2026 brackets.

If you have, say, $2–3 million of traditional retirement accounts, putting everything into traditional accounts today may create a surprisingly large future tax bill.

Conversely, if you'll have a modest traditional balance and mostly Social Security plus taxable/Roth assets, traditional contributions today can be extremely efficient.

My default for a two-income couple

Absent other information, I'd consider a barbell approach:

• Higher-income spouse: primarily traditional 401(k)
• Lower-income spouse: primarily Roth 401(k)
• Both: enough traditional to capture valuable deductions, enough Roth to build meaningful tax-free assets
• As retirement approaches: gradually evaluate whether additional Roth conversions make sense

The optimal split can be quite different depending on your actual numbers.

If you give me each spouse's age, salary, current 401(k)/IRA balances, approximate retirement age, expected Social Security/pension income, and whether you expect income to rise or fall, I can calculate a much more concrete e.g. “Spouse A 80% traditional / 20% Roth, Spouse B 30% traditional / 70% Roth” recommendation using the 2026 brackets.

When deciding how a couple should split contributions between a Roth 401(k) and a Traditional 401(k) , the core mechanism comes down to comparing your current marginal tax bracket with your expected future marginal tax bracket in retirement.

Here is how you should evaluate and split your contributions:

• Current Bracket vs. Future Bracket: If your current marginal tax bracket is higher than what you expect in retirement, favor Traditional contributions to get an immediate tax deduction now. If your current bracket is lower or equal to what you expect later (or if you anticipate tax rates rising overall), favor Roth contributions to lock in today's lower rates.
• Tax Diversification (The "Both" Strategy): Most couples benefit from contributing to both types of accounts. This creates tax flexibility in retirement, allowing you to withdraw from Traditional accounts to fill up lower tax brackets (10%, 12%, 22%, etc.) and use Roth withdrawals for large, unexpected expenses without pushing yourself into a higher tax bracket.
• Income Levels and Career Trajectory: If one partner earns significantly more than the other, the higher earner might lean heavily into Traditional 401(k) contributions to lower their higher marginal rate, while the lower earner contributes more to a Roth 401(k) since they are in a lower current bracket.
• Employer Match Rules: Note that under federal rules, employer matching contributions to a 401(k) are legally required to go into a Traditional pre-tax account, even if your personal employee contributions go into a Roth 401(k). Keep this in mind when calculating your total pre-tax vs. post-tax balance.
• Required Minimum Distributions (RMDs): Traditional 401(k)s are subject to RMDs starting at age 73 (moving to 75 depending on birth year under SECURE 2.0 rules), which can force taxable income upon you later. Roth 401(k)s no longer have RMDs during the original account holder's lifetime, making Roth a powerful tool to manage future RMD pressure.

To help tailor this strategy, could you share:

• Your approximate combined household income and current filing status
• How many years until retirement you both have
• Whether you expect your retirement income to be higher, lower, or similar to today

I can help you map out an exact percentage split for your contributions.

For a couple, the key question is “What marginal tax rate are we avoiding today by using traditional, versus what tax rate are we likely to pay on that money later?” You don't necessarily want both spouses making the same choice.

For 2026, married couples filing jointly have federal marginal brackets of 10%, 12%, 22%, 24%, 32%, 35%, and 37%. The 22% bracket runs from $100,800 to $211,400 of taxable income, and the 24% bracket from $211,400 to $403,550.

A practical way to split it

• If you're currently in the 10% or 12% bracket: Favor Roth 401(k) heavily. Paying 10–12% now for tax-free qualified withdrawals later is generally attractive.
• If you're in the 22% bracket: This is the gray zone. A mix of Roth and traditional is often sensible, particularly if you expect substantially higher income later.
• If you're in the 24% bracket: I'd generally lean traditional 401(k), unless you have strong reasons to expect your retirement marginal rate to be at least 24% or higher.
• If you're in the 32%+ brackets: Traditional is usually particularly attractive because you're getting a large tax deduction today. You can then potentially withdraw the money in retirement at lower rates.
• If one spouse earns substantially more than the other: Consider having the higher earner favor traditional while the lower earner favors Roth. This can create useful tax diversification without requiring an all-or-nothing decision.

Why the couple's situation matters

Suppose one spouse is earning $250,000 and the other $75,000. If they file jointly, they're looking at roughly $325,000 of gross income before deductions and adjustments. Much of their marginal income may fall in the 24% bracket.

In that situation, I'd generally consider something like:

Higher earner: 70–100% traditional Lower earner: 50–100% Roth

That's not a magic formula—it is a way to deliberately get both a current tax deduction and a pool of future tax-free money.

Conversely, if you're early in your careers and currently in the 12% or 22% range but expect promotions to put you into 32%+ territory later, I'd lean more Roth now, then gradually switch toward traditional as your income rises.

Don't forget the retirement tax picture

The biggest mistake is comparing today's tax bracket with the tax bracket on your entire retirement income. Traditional 401(k) withdrawals are taxed as ordinary income, but your retirement income may be considerably lower than your working income.

For example, if you're currently paying 24% on your next dollar but expect retirement taxable income to put your next dollar in the 12% or 22% bracket, traditional is potentially a very good trade.

On the other hand, Roth becomes especially valuable if you expect:

• substantial pensions or other guaranteed income;
• large traditional 401(k)/IRA balances;
• high retirement spending;
• significant future tax-rate increases;
• or a desire for tax-free income flexibility in retirement.

A Roth/traditional combination also gives you flexibility: in a low-income retirement year, you can take more from traditional accounts; in a high-income year, you can draw from Roth.

One important 2026 wrinkle

The employee 401(k) contribution limit is $24,500 per person in 2026, with additional catch-up amounts for eligible older workers.

So if both spouses have access to 401(k)s, you're potentially deciding how to allocate up to $49,000/year between Roth and traditional, before catch-ups.

Also, starting in 2026, certain catch-up contributions must be Roth for workers whose prior-year wages with that employer exceeded $150,000, if the plan offers a Roth feature.

The simplest rule I'd use

Think of each spouse's contributions in tax-rate buckets:

Then adjust based on expected retirement income.

If you give me each spouse's approximate salary, age, current 401(k) balance, expected retirement age, and rough expected retirement income, I can show you a concrete Roth/traditional percentage split for each spouse and explain the tax math behind it.

Deciding how to split contributions between a Roth and a Traditional 401(k) comes down to a fundamental tax comparison: paying taxes now at your current marginal rate versus deferring taxes to pay your ordinary income tax rate in retirement.

Here is how a couple should evaluate their split based on current and expected future tax brackets:

• Current Tax Bracket vs. Future Bracket: If your current marginal tax bracket is lower than what you expect it to be in retirement (due to lower current income or anticipated future tax law changes), favor the Roth 401(k) . If your current bracket is higher than your expected retirement bracket, favor the Traditional 401(k).
• Tax Diversification (The "Hedge"): Because nobody can predict future tax policy or their exact retirement lifestyle expenses, contributing to both provides flexibility. It allows you to withdraw from Traditional accounts to fill up lower tax brackets in retirement, and pull from Roth accounts to fund extra expenses without bumping into a higher tax bracket.
• High Earners in Peak Earning Years: If a couple is in the top marginal tax brackets (e.g., 37% or 35%), the immediate tax deduction of a Traditional 401(k) usually outweighs the long-term tax-free growth of a Roth, because saving thousands of dollars in taxes today provides immediate cash flow.
• Early Career or Lower/Moderate Earners: If they are in the 10%, 12%, or 22% tax brackets, paying the tax now via a Roth 401(k) is often a bargain, as they are locking in historically low tax rates.
• RMD Management (Required Minimum Distributions): Traditional 401(k)s force withdrawals later in life (RMDs), which can inadvertently spike your retirement tax bracket. Adding Roth 401(k) contributions reduces future RMD pressure since Roth 401(k) accounts no longer have RMDs as of recent legislation.

If you want to tailor this strategy, tell me:

• Your current combined annual income
• Your expected retirement age or timeline
• Roughly how much you have saved in Traditional vs. Roth accounts so far

I can help you map out a more precise percentage split.

Deciding between Roth and traditional 401(k) contributions comes down to a comparison of your current marginal tax bracket versus your expected future marginal tax bracket in retirement.

Here is how you should think about splitting your contributions based on tax bracket dynamics:

• The Golden Rule
  • Current tax rate < Future tax rate: Choose Roth contributions (pay the lower tax rate now).
  • Current tax rate > Future tax rate: Choose Traditional contributions (take the tax deduction now at your higher rate).
  • Current tax rate ≈ Future tax rate: The math yields the same net result, meaning the decision hinges on diversification or flexibility.
• Why a Split (Tax Diversification) Makes Sense
  • Hedge against uncertainty: Tax laws change, and it is impossible to predict your exact future income, future required minimum distributions (RMDs), or what tax brackets will look like decades from now.
  • Control over taxable income in retirement: Having both buckets gives you a "dual-control valve." You can withdraw from your Traditional 401(k) up to the top of a lower tax bracket, and then pull from your Roth account for extra spending without bumping yourself into a higher bracket.
  • Managing IRMAA and Social Security: A mix allows you to manage Medicare premium surcharges (IRMAA) and how much of your Social Security benefits get taxed in retirement.
• How to Strategically Split Your Contributions
  • By Income Tier (The High Earner Split): If one spouse earns significantly more and is in a high tax bracket (e.g., 32 percent or 35 percent), that spouse should lean heavily or exclusively into Traditional 401(k) to get the maximum deduction. If the other spouse earns less and is in a lower bracket (e.g., 12 percent or 22 percent), they should lean into Roth.
  • The 50/50 or Percentage Balance: If both partners are in the same moderate tax bracket (e.g., 22 percent or 24 percent) and expect a similar lifestyle in retirement, a clean split—such as 50% Roth and 50% Traditional, or 70/30—builds immediate tax diversification without over-committing to either scenario.
  • Prioritize the Match First: Always contribute enough to your 401(k) to get the full employer match, regardless of whether it goes to Roth or Traditional. (Note: Under SECURE 2.0 rules, employer matches can now be deposited as Roth, though plan adoption varies).

To help tailor this split for your specific situation, tell me:

• Your combined annual household income and your current tax bracket
• Your approximate age and target retirement age
• Whether you expect your retirement income to be higher, lower, or similar to what you make now

The key is to compare your marginal tax rate on the next dollar contributed today with the marginal tax rate you expect to pay on that dollar when withdrawn.

For a couple, I’d generally approach it this way:

1. Use traditional 401(k) when today's marginal rate is high

Traditional contributions reduce taxable income now; withdrawals are generally taxable later. Roth contributions are taxed now, but qualified withdrawals are tax-free.

For 2026 married-filing-jointly, the federal brackets are:

So, for example, if a couple is currently in the 24% marginal bracket but expects retirement income to put them mostly in the 12% or 22% brackets, traditional 401(k) contributions are particularly attractive: they're getting a 24% deduction today and potentially paying a lower rate later.

Conversely, if they're currently in the 12% or 22% bracket and expect substantial retirement income—pensions, Social Security, large traditional accounts, real estate income, etc.—Roth becomes much more attractive.

2. Don't necessarily make the same choice for both spouses

This is an important opportunity for couples.

Suppose:

• Spouse A earns $250,000 and is effectively in the 24% marginal bracket.
• Spouse B earns $60,000 and is effectively in the 12% bracket.
• They expect both to have substantial retirement income.

Rather than automatically doing 50/50 Roth/traditional, I'd lean toward:

Spouse A → predominantly traditional
Spouse B → predominantly Roth

That lets you capture the valuable high-bracket deduction from A while buying relatively inexpensive tax-free space for B.

The IRS explicitly allows an employee to split their own elective deferrals between traditional and Roth in whatever proportion the plan permits.

3. A useful rule of thumb

Think of the current marginal rate versus expected retirement marginal rate:

The "mix" can be valuable because you're not really trying to predict taxes 30 years from now with precision—you can instead create tax diversification.

4. For many couples, I'd favor a mix rather than an all-or-nothing decision

Having both traditional and Roth money gives you flexibility in retirement.

For example, you could withdraw enough traditional money to fill a lower tax bracket and then take additional spending from Roth without increasing taxable income. Roth qualified distributions aren't included in taxable income.

That flexibility can also matter for things whose costs depend on taxable income.

A practical way to set the split

I'd start with this sequence:

1. Both spouses contribute enough to get the full employer match.
2. Determine each spouse's marginal federal + state tax rate today.
3. Estimate retirement taxable income before withdrawals from the 401(k)s.
4. Estimate the marginal rate at which additional traditional withdrawals would be taxed.
5. Put more traditional money in the higher-current-bracket spouse's 401(k) when today's rate materially exceeds the expected retirement rate.
6. Put more Roth money in the lower-current-bracket spouse's 401(k) when today's rate is unusually low relative to what you expect later.
7. If the future is genuinely uncertain, deliberately maintain both Roth and traditional balances rather than betting everything on one tax regime.

One subtle point: compare equivalent amounts of after-tax money, not simply "$10,000 Roth vs. $10,000 traditional." A $10,000 traditional contribution costs less in take-home pay today because it receives the tax deduction. That matters when doing the long-term math.

If you give me both spouses' incomes, filing status, state, ages, current 401(k) balances, annual contributions, and approximate retirement income, I can calculate a much more concrete Roth/traditional percentage for each spouse using the 2026 brackets.

For a couple, the key question is “Are we better off paying tax on this dollar now or later?” The answer should be based on your marginal tax rate today versus the likely marginal rate on withdrawals in retirement, not simply on whether you expect taxes to rise.

A practical way to split Roth vs. traditional

For 2026, married filing jointly has these federal marginal brackets: 22% begins at $100,800 of taxable income, 24% at $211,400, 32% at $403,550, 35% at $512,450, and 37% at $768,700. The standard deduction is $32,200.

The reason is that a traditional contribution gives you a tax deduction at your current marginal rate, while Roth contributions are taxed now and potentially withdrawn tax-free later. The IRS confirms that Roth 401(k) and traditional 401(k) contributions share the same employee-deferral limit; in 2026 that's $24,500 per person, before applicable catch-ups.

The couple-specific wrinkle

Don't necessarily make the same Roth/traditional percentage for both spouses.

Suppose:

• Spouse A earns $200k
• Spouse B earns $80k
• You're married filing jointly
• You expect both to have substantially lower individual taxable income in retirement.

Spouse A may want to favor traditional, because deductions are saving taxes at relatively high marginal rates. Spouse B could favor Roth, particularly if their income falls into the 12% or lower portion of the joint return.

That gives you tax diversification: a pool of traditional money to exploit lower retirement brackets, plus Roth money that can be withdrawn without increasing taxable income.

A particularly useful strategy

Rather than deciding “we're 70% Roth people,” consider filling tax brackets deliberately.

For example, if you're comfortably into the 24% bracket but have room before reaching 32%, you might make enough traditional contributions to keep taxable income from entering the 32% bracket, while directing additional retirement savings to Roth.

Conversely, if you're currently in the 22% bracket and expect to retire in the 24%+ range, Roth becomes considerably more attractive.

Don't overlook retirement-income planning

Your future tax rate isn't necessarily your current salary tax rate. In retirement, you'll potentially have:

• Social Security
• traditional 401(k)/IRA withdrawals
• pensions
• investment income
• Roth withdrawals
• required minimum distributions
• potentially Medicare-related income thresholds

Having both traditional and Roth assets gives you flexibility to choose where retirement income comes from each year.

That's why I generally wouldn't recommend going 100% traditional or 100% Roth unless the tax-rate difference is unusually compelling.

One other 2026 wrinkle: for participants subject to the new SECURE 2.0 catch-up rule, certain higher-paid workers must make catch-up contributions on a Roth basis if their prior-year wages from the employer exceeded $150,000.

If you give me 5 numbers, I can make this much more precise

Send me:

1. Each spouse's annual income
2. Each spouse's current 401(k) contribution
3. Your approximate current 401(k)/IRA balances
4. Your expected retirement age
5. Roughly how much you expect to spend per year in retirement

I can then estimate your current marginal bracket, likely retirement bracket, and give you a specific Roth/traditional percentage for each spouse rather than a generic rule.

Deciding how a couple should split their 401(k) contributions between Roth and Traditional depends on a simple core principle: comparing your current marginal tax bracket to your expected future marginal tax bracket in retirement.

Here is a clear breakdown of how to evaluate your brackets and strategically split your contributions.

1. The Core Decision Rule

• Current Bracket > Future Bracket: Favor Traditional (pre-tax) contributions. You get a tax break today when your income is higher, and you pay less tax later when withdrawing in a lower bracket.
• Current Bracket < Future Bracket: Favor Roth (after-tax) contributions. You pay taxes now at a lower rate, locking in tax-free growth and tax-free withdrawals later when your bracket is higher.
• Current Bracket ≈ Future Bracket: It is largely a tie mathematically , making it a great opportunity for tax diversification (holding a mix of both).

2. Strategic Split Frameworks

If you are unsure where your future tax bracket will land—or if you expect it to be similar—using a split strategy provides flexibility.

• • 50/50 Split: Equal contributions to both Traditional and Roth 401(k) accounts. This provides a balanced hedge against future tax law changes and gives you control over your taxable income in retirement.
• • Bracket Filling Strategy: Contribute to Traditional enough to bring your taxable income down to the bottom edge of your current tax bracket (or drop down a bracket threshold), then allocate the remainder to Roth.
• • Income-Tier Split (for couples with unequal earnings): The higher earner contributes to Traditional (maximizing the deduction at the highest marginal rate), while the lower earner contributes to Roth (paying a lower rate now while building a tax-free bucket).

3. Key Factors to Consider for the Future

When estimating your future tax bracket, account for these variables:

• Required Minimum Distributions (RMDs): Large Traditional balances will force large RMDs later in life, which can push you into a higher-than-expected bracket, especially when combined with Social Security and pensions.
• Future Tax Policy: Federal income tax brackets are scheduled to revert to higher pre-2018 levels after 2025 unless extended, meaning future rates could be higher overall.
• Lifestyle Changes: Expenses often drop in retirement (no mortgage, no commuting costs, no saving for retirement), which typically lowers your required annual income and tax bracket.

If you share your approximate household income , your current state of residence , and how many years until retirement , I can help you estimate your current vs. future bracket math.

The best split between Roth 401(k) and traditional (pre-tax) 401(k) contributions depends mainly on one comparison:

Are your current marginal tax rates higher or lower than the tax rates you expect to face when you withdraw the money?

A traditional 401(k) gives you a tax break today and taxes withdrawals later. A Roth 401(k) taxes you today, but qualified withdrawals are generally tax-free.

A practical decision framework for a couple

A common couple strategy

Many couples do not choose 100% one way. A typical approach:

1. Get the full employer match first (regardless of Roth vs. traditional).
2. Put enough traditional 401(k) money in to reduce today’s income if you are in a high bracket.
3. Put the remainder into Roth to build a pool of tax-free retirement money.

Examples:

Example A: Young couple, currently in 12%–22% brackets

• Expected careers will increase income substantially.
• Retirement may involve high withdrawals.

Possible split:

• 70–100% Roth 401(k)
• 0–30% traditional

Example B: Couple currently in 24%–32% brackets

• Expect retirement spending to be lower than working income.

Possible split:

• 60–90% traditional
• 10–40% Roth

Example C: High earner + lower earner

• Spouse A: $200k income
• Spouse B: $60k income

A reasonable starting point might be:

• Higher earner: mostly traditional (capture deductions at a higher marginal rate)
• Lower earner: more Roth (pay taxes at a lower bracket)

A useful “tax bracket arbitrage” rule

Think in terms of marginal rates:

• If you save $10,000 in a traditional 401(k) while paying a 32% marginal tax rate, you avoid about $3,200 of current federal tax.
• If you later withdraw that money when your effective retirement tax rate is 15%, traditional wins.
• If you contribute while paying 12% and later withdraw while paying 25%, Roth likely wins.

Why a mix is often valuable

A retirement portfolio with both account types gives flexibility:

• Withdraw traditional money up to a desired tax bracket.
• Use Roth money for large expenses without increasing taxable income.
• Potentially manage taxes related to Social Security, Medicare premiums, and required minimum distributions.

A traditional-only strategy can create a large taxable balance later; a Roth-only strategy can mean paying today’s higher tax rates unnecessarily.

To tailor the split, the key inputs are:

1. Your combined household income and filing status.
2. Your current federal/state marginal tax bracket.
3. Ages of both spouses.
4. Expected retirement income (pensions, Social Security, rental income, business income).
5. Whether you expect your income to rise significantly.

If you provide those numbers, I can suggest a more specific Roth/traditional percentage split.

When a couple is deciding how to split their 401(k) contributions between Traditional (pre-tax) and Roth (after-tax) accounts, the most mathematically sound approach isn't an arbitrary 50/50 split. Instead, it is an opportunistic sliding scale based on their current marginal tax bracket compared to their anticipated retirement tax bracket , combined with a strategy for building tax diversification.

The total combined employee contribution limit for a 401(k) is $24,500 (plus catch-up allowances if age 50+ or 60–63), and couples can divvy up these caps across both bucket types however they choose.

The Bracket-Based Decision Framework

1. Low Brackets (10% and 12% equivalents) → 100% Roth
   • Why: If the couple's combined income places them in the lowest tax brackets, paying the tax bite now is a bargain. It is statistically rare to encounter a marginal tax bracket lower than 12% in retirement once you factor in Social Security or baseline living expenses.
2. Middle Brackets (22% and 24%) → The Strategic Split (e.g., 50/50 or Bracket-Capping)
   • Why: This is the "uncertainty zone". Because future tax law changes and individual retirement spending are unpredictable, splitting contributions hedges your bets. A smart tactic here is using Traditional 401(k) dollars to siphon off income at the top of the bracket, keeping taxable income right at the threshold of the lower bracket, and routing the remaining savings capacity to Roth.
3. Peak Earning Brackets (32% and higher) → 100% Traditional
   • Why: Getting an immediate 32% or 35%+ tax deduction is a massive win. In retirement, it is highly likely the couple's taxable withdrawals will fill up lower brackets from the bottom up, meaning those high-earning current dollars would be taxed at a significantly lower rate later.

Key Tactical Rules for Couples

• Capture the Match First: If the employer offers a match, take it. Note that employer matching contributions always go into a Traditional (pre-tax) account by law, meaning a couple who chooses 100% Roth employee contributions will still end up with natural tax diversification because of the pre-tax match.
• Mind the SECURE 2.0 Catch-Up Rule: If either spouse is age 50 or older and earned more than $150,000 in FICA wages from the employer in the prior year, any catch-up contributions must be directed into the Roth bucket. Factor this mandatory Roth allocation into the overall percentage split.
• The Power of Future Flexibility: Having a mix of both buckets gives the couple absolute control in retirement. They can pull fluid amounts from the Traditional side to fill low tax brackets, and tap the Roth side for major, lumpy expenses (like a new car, roof, or medical costs) without triggering a jump in their marginal tax bracket or triggering Medicare IRMAA surcharges.

If you share your approximate combined household income and current filing state , I can help map out a more precise percentage split recommendation for your tax situation.