Do You Pay Capital Gains Tax on 401(k) Withdrawals?

Do You Pay Capital Gains Tax on 401(k) Withdrawals?

The short answer: no. The 401k capital gains tax question trips up a surprising number of high earners, but the mechanics are straightforward once you understand them. Distributions from a traditional 401(k) are taxed as ordinary income, not as capital gains. The more consequential question is how much ordinary income tax you will owe, and whether your current strategy is doing anything to reduce it.

For someone holding $5M or more in a traditional 401(k), the difference between a well-structured withdrawal plan and a passive one can easily exceed seven figures over a 20-year retirement. The rules are fixed. The strategy is not.

How 401(k) Accounts Are Actually Taxed

Under IRC Section 402(a), amounts distributed from a qualified retirement trust are includible in the gross income of the distributee in the taxable year received, and they are treated as ordinary income rather than capital gain. The IRS makes no distinction between the portion of your distribution that represents original contributions and the portion that represents decades of compounded growth. It all comes out as ordinary income.

This is a direct consequence of the pre-tax structure. You deferred taxes on the way in, so the IRS collects on the way out. Every dollar, whether it came from your 1995 contribution or a stock that tripled inside the account, gets taxed at your marginal rate in the year of distribution.

The IRS confirms this treatment in Publication 575, which governs pension and annuity income. There is no preferential rate for long-term holding periods inside a qualified plan. A stock you have held inside your 401(k) for 30 years does not qualify for the 0%, 15%, or 20% long-term capital gains rates that would apply to the same stock held in a taxable brokerage account.

This is the core distinction that matters for taxation of non-retirement investment accounts: in a taxable account, you pay capital gains rates on appreciation. In a traditional 401(k), you pay ordinary income rates on everything.

The One Exception: Net Unrealized Appreciation

The claim that 401(k) distributions are never subject to capital gains rates is technically incomplete. There is one legitimate exception: Net Unrealized Appreciation, or NUA.

If you hold highly appreciated employer stock inside your 401(k) and take a lump-sum distribution, you can distribute that stock in-kind rather than liquidating it. You pay ordinary income tax only on the original cost basis of the shares. The appreciation, the NUA, is then subject to long-term capital gains rates when you eventually sell the shares, regardless of how long you hold them after distribution.

For a tech executive or long-tenured employee who accumulated employer stock over decades, the NUA strategy can represent a six- or seven-figure tax savings opportunity. If your cost basis is $200,000 and the current value of the stock is $2M, you pay ordinary income tax on $200,000 and long-term capital gains rates on $1.8M. At a 20% capital gains rate versus a 37% marginal rate, that differential is meaningful.

The SEC's investor guidance on NUA notes that this strategy requires a qualifying triggering event, typically separation from service, reaching age 59½, disability, or death. It also requires a lump-sum distribution of the entire plan balance in a single tax year. Partial distributions do not qualify.

NUA is worth modeling carefully with your tax attorney before you separate from service. Once you roll the stock into an IRA, you permanently lose the NUA treatment.

2025 Contribution Limits: What High Earners Need to Know

Before addressing withdrawal strategy, it is worth confirming you are maximizing the accumulation side. According to IRS Notice 2024-80, the 2025 contribution limits are as follows:

The enhanced catch-up limit for ages 60 to 63 is a SECURE 2.0 provision that took effect in 2025. If you are in that window, you should be using it.

For self-employed FATFIRE individuals, the Solo 401(k) remains one of the most efficient vehicles available. As both employee and employer, you can contribute up to 25% of net self-employment income on the employer side, stacking on top of the employee deferral. The Congressional Research Service's summary of SECURE 2.0 notes that the legislation also expanded Solo 401(k) provisions for self-employed individuals, making these plans more flexible than they were under prior law.

The Mega Backdoor Roth: The Strategy Most Plans Don't Advertise

For high earners who have already maxed their standard 401(k) deferral, the mega backdoor Roth is one of the few remaining high-capacity tax-advantaged strategies. The mechanics depend on a specific plan feature that most participants never think to check.

The 2025 total 415(c) limit is $70,000. The employee deferral limit is $23,500. The gap, up to $46,500, can potentially be filled with after-tax (non-Roth) contributions if your plan document explicitly permits them. Once those after-tax contributions are in the plan, you can convert them to Roth through either an in-plan Roth conversion or an in-service withdrawal to a Roth IRA.

The result: up to $46,500 per year in additional Roth contributions, far exceeding the $7,000 direct Roth IRA limit, with no income restriction.

The critical nuance is plan-document dependency. Vanguard's 2024 "How America Saves" data shows that only 14% of eligible participants utilized after-tax contributions in plans that allow them, which suggests the strategy is significantly underutilized even among high-income savers. The first step is confirming whether your plan allows after-tax contributions and in-service distributions or in-plan conversions. Many large employer plans do not. If yours does not, this is worth raising with your CFO or benefits administrator, particularly if you have influence over plan design.

For more on maximizing Roth deferral contributions within your current plan structure, the mechanics of in-plan conversions are worth understanding before year-end.

How Required Minimum Distributions Affect High-Net-Worth Retirees

RMDs are the most consequential and underplanned tax issue for FATFIRE individuals with large traditional 401(k) balances. Under SECURE 2.0, the required beginning date is now age 73 for individuals born between 1951 and 1959, and age 75 for those born in 1960 or later, per IRS Publication 590-B.

The math is stark. A retiree with $5M in a traditional 401(k) at age 75 faces an IRS Uniform Lifetime Table divisor of approximately 27.4. That produces a required distribution of roughly $182,500 in the first year, before accounting for any other income. Add Social Security, taxable account income, or rental income, and you are likely looking at a marginal federal rate of 32% to 37%, plus potential Medicare IRMAA surcharges.

At $10M, the forced distribution exceeds $365,000. The account continues growing, so the RMD grows with it. This is the tax time bomb that accumulates silently while you are focused on building the portfolio.

SECURE 2.0 eliminated RMDs for Roth 401(k) accounts starting in 2024, which is a significant structural advantage for Roth balances. Traditional 401(k) balances still carry the full RMD obligation.

The practical implication: if you retire before age 73 or 75, you have a window to reduce the traditional 401(k) balance before RMDs begin. How you use that window determines a substantial portion of your lifetime tax bill.

Roth Conversion Strategy: Using the Pre-RMD Window

The years between early retirement and RMD onset are the most tax-efficient planning window most high-net-worth retirees will ever have. Income drops, marginal rates drop, and the clock is running on a tax-deferred balance that will eventually force distributions at whatever rate Congress sets.

Research published in the Journal of Financial Planning demonstrates that systematic Roth conversions during this window can meaningfully reduce lifetime tax liability for high-net-worth individuals by filling lower marginal tax brackets before RMDs force income into higher ones.

The strategy: each year before RMDs begin, convert enough of your traditional 401(k) or IRA balance to Roth to fill your current marginal bracket without crossing into the next one. You pay tax now at a known rate rather than later at an unknown (and potentially higher) rate. The converted balance grows tax-free and carries no RMD obligation.

For a concrete illustration, consider three scenarios for a retiree with a $5M traditional 401(k) balance at age 62, retiring with no other earned income:

The right conversion rate depends on your other income sources, state tax situation, IRMAA thresholds, and estate planning objectives. The point is that doing nothing is itself a choice, and usually not the optimal one.

For a detailed look at converting a 401(k) to a Roth IRA, including the mechanics of direct rollovers and the tax withholding traps to avoid, the execution details matter as much as the strategy.

The Pro-Rata Rule and the Backdoor Roth Trap

High earners who exceed the Roth IRA income limits ($165,000 single, $246,000 married in 2025) typically attempt backdoor Roth contributions: contribute to a non-deductible traditional IRA, then convert to Roth. The strategy works cleanly only if you have no other pre-tax IRA balances.

Under IRC Section 408 (the pro-rata rule), the IRS treats all your traditional IRA balances as a single pool when calculating the taxable portion of a conversion. If you have $950,000 in a rollover IRA and $50,000 in a non-deductible IRA, and you convert the $50,000 non-deductible contribution to Roth, 95% of that conversion is taxable. You cannot selectively convert only the after-tax dollars.

The workaround: roll your pre-tax IRA balance into your current employer's 401(k) before executing the backdoor Roth. This clears the IRA balance, leaving only the non-deductible contribution to convert. Not all 401(k) plans accept incoming rollovers, so this requires a plan that does.

This is a nuance that catches many high earners who read generic backdoor Roth guidance written for people without significant rollover IRA balances. The optimal allocation between Roth and 401(k) depends heavily on whether you can execute the pro-rata workaround cleanly.

Traditional vs. Roth vs. Taxable: Tax Treatment Comparison

Understanding where each account type fits in a broader portfolio requires clarity on how each is taxed at every stage.

For how retirement income is taxed across account types, including the interaction between Social Security, RMDs, and IRMAA thresholds, the sequencing of withdrawals across these buckets is where most of the planning leverage sits.

Strategic Withdrawal Sequencing in Retirement

The order in which you draw down accounts in retirement has a direct impact on your lifetime tax bill. The conventional guidance (taxable first, then tax-deferred, then Roth) is a reasonable default, but it is not optimal for everyone at the FATFIRE level.

Standard 60/40 withdrawal guidance ignores someone with a $3M taxable brokerage account, a $5M traditional 401(k), and a $1M Roth. The interaction between those balances, RMDs, Social Security timing, and IRMAA brackets requires a more granular approach.

A few principles that hold across most high-net-worth situations:

Delay Social Security to 70. This maximizes the inflation-adjusted benefit and reduces the pressure to draw from tax-deferred accounts early.

Use the pre-RMD window for Roth conversions. As discussed above, this is the primary lever for reducing the eventual RMD burden.

Coordinate taxable account harvesting with 401(k) distributions. In years when you take large 401(k) distributions, you may be in a bracket where capital losses from taxable accounts can offset other income. The coordination between accounts matters.

Model IRMAA thresholds explicitly. Medicare Part B and Part D surcharges kick in at modified adjusted gross income above $106,000 (single) or $212,000 (married) in 2025. A Roth conversion that pushes you $10,000 over a threshold can cost several thousand dollars in additional premiums. These are cliffs, not slopes.

For a structured framework on strategic withdrawal sequencing from retirement accounts, the specific order and amounts matter more than most people realize until they are already in retirement.

State Tax Considerations for 401(k) Distributions

Federal tax gets most of the attention, but state income tax on 401(k) distributions can represent a material cost over a multi-decade retirement. The variation across states is significant enough to factor into retirement domicile decisions.

California taxes 401(k) distributions as ordinary income with no special retirement income exclusion, at rates up to 13.3%. Illinois, Mississippi, and Pennsylvania exempt most or all retirement income from state income tax. Several other states offer partial exemptions or credits.

For a $5M traditional 401(k) generating $200,000 in annual distributions, the difference between retiring in California and retiring in a no-tax state like Florida or Texas is roughly $26,600 per year at the top California rate. Over 20 years, that is more than $500,000 in additional state tax, before accounting for growth.

This is not an argument to move purely for tax reasons. But if you are already considering a retirement location change, the state tax treatment of retirement income deserves explicit modeling alongside property taxes, cost of living, and estate tax exposure.

The tax strategy changes in retirement that matter most are often the ones that interact across multiple jurisdictions and income sources simultaneously.

Early Withdrawal Penalties and the 72(t) Exception

Withdrawals from a traditional 401(k) before age 59½ trigger a 10% early withdrawal penalty under IRC Section 72(t), on top of ordinary income tax. At a 37% marginal rate, an early withdrawal carries an effective tax cost of 47% before state taxes. That is a high bar to clear.

The 72(t) exception, also called Substantially Equal Periodic Payments (SEPP), allows penalty-free early withdrawals if you commit to a fixed payment schedule for the longer of five years or until you reach age 59½. The payment amount is calculated using one of three IRS-approved methods (required minimum distribution, fixed amortization, or fixed annuitization) and cannot be modified once started without triggering retroactive penalties.

For FATFIRE individuals who retire early, the 72(t) strategy is worth modeling carefully. It provides access to 401(k) funds without penalty, but the inflexibility is real. Once you start a SEPP schedule, you are locked in. A large unexpected expense or a change in tax law can make the fixed payment suboptimal, and you cannot adjust without penalty.

The Roth conversion ladder is often a more flexible alternative for early retirees: convert traditional 401(k) funds to Roth IRA over several years, then withdraw the converted principal (not earnings) tax-free and penalty-free after a five-year seasoning period. This requires more upfront planning but preserves flexibility.

For context on capital gains taxation on deferred compensation and how early distribution rules interact with non-qualified deferred comp plans, the rules differ meaningfully from qualified 401(k) plans.

Inherited 401(k) Accounts and the 10-Year Rule

If you are planning to pass a 401(k) to heirs, the post-SECURE Act rules significantly changed the calculus. Most non-spouse beneficiaries are now subject to the 10-year rule: the entire inherited account must be distributed within 10 years of the original owner's death. There is no option to stretch distributions over the beneficiary's lifetime, as was possible before 2020.

For a beneficiary inheriting a $3M traditional 401(k), the 10-year rule forces roughly $300,000 per year in distributions, potentially stacking on top of the beneficiary's own earned income and pushing them into the top marginal bracket. The tax efficiency of the inherited account deteriorates rapidly.

Roth 401(k) balances passed to heirs are subject to the same 10-year distribution rule, but the distributions remain tax-free. This makes Roth balances significantly more valuable as an inheritance vehicle than traditional balances of the same nominal size.

For estate planning purposes, inherited Roth 401(k) tax implications are worth reviewing with your estate attorney, particularly if your estate plan relies on retirement accounts as a primary wealth transfer mechanism.

References

• Internal Revenue Service, "Publication 575: Pension and Annuity Income" (2024).
• Internal Revenue Service, "IRC Section 402(a): Taxability of Beneficiary of Exempt Trust" (current).
• Internal Revenue Service, "IRS Notice 2024-80: 401(k) Limit Increases to $23,500 for 2025, IRA Limit Remains $7,000" (2024).
• Internal Revenue Service, "Publication 590-B: Distributions from Individual Retirement Arrangements (IRAs)" (2024).
• Internal Revenue Service, "IRC Section 72(t): 10% Additional Tax on Early Distributions" (current).
• Vanguard, "How America Saves 2024" (2024).
• Journal of Financial Planning, "Optimal Roth Conversion Strategies for High-Net-Worth Retirees" (2023).
• Congressional Research Service, "SECURE 2.0 Act of 2022 (Division T of P.L. 117-328): Summary of Key Provisions" (2023).