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Accounts · Lots of talk

Mega backdoor Roth

Also called after-tax 401k · mega backdoor · in-plan Roth conversion · after tax conversion

Community talk. May contain inaccuracies. Not financial, tax, legal, or investment advice. No return or outcome is promised.

A mega backdoor Roth moves a workplace plan’s separate after-tax contributions into a Roth retirement account. People use it to save more for retirement beyond their ordinary 401(k) deferrals. It requires specific employer-plan features; a Roth option alone is not enough.

Fidelity · 2026

01

The contribution, then the Roth move

There are three different contribution types. Ordinary pre-tax deferrals postpone income tax; ordinary Roth deferrals pay it now. Both use the employee deferral limit. Separate non-Roth after-tax contributions use already-taxed pay, but their earnings are pretax money. Those separate contributions are the starting point here.

Fidelity · 2026

Confirm both the contribution and an available Roth route. The summary plan description explains the features. Ask the administrator whether separate after-tax contributions are allowed, then whether they can move to Roth inside the plan or through a rollover while still employed. Either route can work. Setup involves payroll elections, conversion instructions, and checking that the first transfer occurred.

Fidelity · 2026

U.S. 2026 limits: $24,500 deferrals; $72,000 total additions. Qualifying catch-up deferrals are separate from that total: $8,000 at age 50 or older, or $11,250 at ages 60–63, if permitted.

IRS · 2026 limits

Employer money reduces the available after-tax room. For an illustrative under-50 employee with sufficient compensation, $24,500 of deferrals and $10,000 from the employer leave $37,500 under the $72,000 ceiling. Count other employer additions and allocated forfeitures too. The total cannot exceed 100% of compensation, and the plan can set a lower limit.

IRS · annual-additions rules

Already-taxed principal and untaxed earnings need different treatment. A rollover distribution generally carries proportional pretax and after-tax amounts. A permitted split can send after-tax principal to a Roth IRA and pretax earnings to a traditional IRA, deferring tax on those earnings. Sending earnings to Roth instead makes them taxable. The administrator must identify the amounts and destinations; requesting only the principal does not remove the allocation rules.

IRS · after-tax rollovers

The deposit and its growth can go to different tax destinations. Illustration: a permitted full distribution of an after-tax source contains $10,000 of contributions and $300 of earnings. If the plan correctly directs the $10,000 to a Roth IRA and $300 to a traditional IRA, the earnings remain tax-deferred. Sending the entire $10,300 to Roth instead brings the $300 of earnings into income. This assumes those are the administrator-confirmed amounts for the distribution. The $300 traditional IRA destination can also affect a separate backdoor Roth calculation later that year.

Illustration · context: Internal Revenue Service

02

Why people use it

More savings can receive Roth treatment. The rollover is separate from an ordinary IRA contribution, so its size is not restricted to the IRA contribution allowance. Available workplace contribution room still controls what can go in.

Fidelity · 2026

Later Roth earnings can be withdrawn tax-free. That requires a qualifying withdrawal. In a Roth workplace account, the usual conditions are five tax years plus age 59½; death or disability can also qualify. This tax treatment does not guarantee investment gains.

IRS · Roth account rules

03

Good to know

Converting does not unlock the money for spending. Plan withdrawal restrictions still matter. Early withdrawals can trigger tax or penalties, and Roth 401(k) and Roth IRA withdrawal rules differ. Check conversion frequency, transaction charges, investment fees, and access before choosing a destination.

IRS · in-plan Roth rules

Plan testing can reduce what highly paid employees keep. After-tax contributions enter the ACP nondiscrimination test, which compares employee groups’ contributions. Where testing applies, a failed test can require refunds or other corrections even below the individual dollar ceiling.

IRS · ACP testing

An IRA destination affects the other backdoor. Pre-tax earnings rolled into traditional, SEP or SIMPLE IRAs enter the year-end pro-rata calculation for regular backdoor Roth conversions. Workplace rollovers follow different rules.

IRS · Form 8606, 2025 instructions

04

From community discussion

Automatic payday conversions saved repeated phone calls. Bogleheads commenters described one call to activate ongoing in-plan conversions; another converted manually each payday. Participants weighing an IRA rollover mentioned repeated security questions and advisor offers during calls. Convenient automation meant keeping the money in the Roth 401(k).

Community · Reddit r/Bogleheads

Quarterly IRA rollovers came with a separate earnings destination. One participant called quarterly, sending principal to a Roth IRA and gains to a traditional IRA, which they later converted. The poster also asked about a different fund mix to reduce pre-conversion earnings; that feature was not established. A reply’s expectation of small quarterly gains was not a guarantee.

Community · Reddit r/Bogleheads

A $20 rollover charge changed the comparison. A personalfinance poster reported quarterly IRA rollovers costing $20 each, versus free automatic in-plan conversions. Replies weighed the plan’s fund choices and withdrawal access. That was one reported fee arrangement, not a current fee schedule for every plan.

Community · Reddit r/personalfinance

An assumed automatic conversion left money waiting for months. A Fire commenter said they owed some tax after discovering conversions were not automatic at their employer. They later called to activate payday conversions. The delay illustrates why a payroll deduction and a completed Roth move are separate checks; the report did not quantify the tax.

Community · Reddit r/Fire

Spreadsheets tracked balances; Form 1099-R caused anxiety. Reports describe spreadsheets separating pre-tax, Roth and non-Roth after-tax money, monthly conversion reminders, and anxiety about the first Form 1099-R. They discuss checking conversion records against the form and involving a tax professional for a large conversion year; receiving the form alone did not mean failure.

Community

A new job sometimes removed the feature entirely. Reports describe rereading plan documents after a job change and at enrollment. Some stopped when the new plan lacked a Roth route, or waited for a permitted rollover event. Others used a taxable brokerage or regular IRA backdoor instead; those alternatives have their own tax and eligibility rules.

Community

Extra Roth saving was optional even in a high-income year. Reports prioritized the match and ordinary retirement saving without diverting rent or emergency cash. Some used this feature only when cash was comfortably available. Their ordering was a budgeting preference, not a rule requiring everyone to max other accounts first.

Community

References for this topic

Sources and context

  1. It’s Official: 457b/401k limit increases to $24,500 ↗

    id
    money-wave-limits-talk — It’s Official: 457b/401k limit increases to $24,500
    role
    Community discussion
    accessed On
    2026-09-23
    locator
    Opening post and replies by Enigma7ic and Kman1287; discussion distinguishing employee limits from other contributions.
    scope
    A higher legal contribution ceiling did not automatically mean a higher affordable paycheck deferral for commenters; one described changing the pre-tax/Roth split.
    limitations
    Selected self-reported public posts and replies, not verified outcomes, a representative sample, a prevalence estimate, or financial/legal proof. No private account material or linked financial screenshots accessed.

  2. Retirement topics: 401(k) and profit-sharing plan contribution limits ↗

    id
    money-wave-limits-rule — Retirement topics: 401(k) and profit-sharing plan contribution limits
    role
    Official context
    accessed On
    2026-09-23
    locator
    2026 elective deferral and annual additions limits.
    scope
    The employee elective-deferral ceiling and combined employee/employer annual-additions ceiling are different limits.
    limitations
    Primary context for the named narrow claim; does not determine an individual account, eligibility or outcome.

  3. Rollovers of after-tax contributions in retirement plans ↗

    id
    money-official-after-tax-rollover — Rollovers of after-tax contributions in retirement plans
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-07
    locator
    After-tax amounts and Roth IRA destination explanation.
    scope
    Checks limited after-tax-to-Roth meaning in mega-backdoor-roth opening.
    limitations
    Primary search text reviewed; not proof that a particular employer plan offers the necessary features, or that a transaction has no tax.

  4. IRS retirement-plan contribution limit table ↗

    id
    quick-irs-retirement2026-total — IRS retirement-plan contribution limit table
    role
    Official context
    accessed On
    2026-09-12
    scope
    2026 defined-contribution overall annual additions limit is $72,000; employee elective-deferral base $24,500; qualifying catch-ups handled separately.
    locator
    Official page or official indexed text read on 2026-09-12.
    limitations
    This reference explains the named format or rule. Individual community accounts remain attributed in the notes.

  5. 401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500 ↗

    id
    money-guide-403b-457-irs-2026 — 401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-24
    locator
    IR-2025-111 highlights for 2026 employee deferrals and catch-up
    scope
    For 2026 the employee deferral for 403(b) and governmental 457 plans is $24,500. Age-50 catch-up is $8,000. The higher catch-up for ages 60 through 63 remains $11,250.
    limitations
    A newsroom summary of Notice 2025-67. It does not describe a nongovernmental 457(b), a match formula, or whether a person should defer.
    slugs
    • four-oh-three-b-457
    • backdoor-roth
    • mega-backdoor-roth
    • roth-vs-traditional
    • lifestyle-creep
    • am-i-behind

  6. What is a mega backdoor Roth? ↗

    id
    money59-mega-backdoor-roth-fidelity-mega — What is a mega backdoor Roth?
    platform
    Fidelity
    role
    Service rules
    accessed On
    2026-09-29
    published Or Updated
    2026-03-23
    locator
    What is it; eligibility; setup; contribution limits
    scope
    Opening, alternate Roth destinations, plan-specific setup and distinction from IRA contributions.
    limitations
    Provider education, not the reader’s plan document. Commercial investment-service context; no product recommendation. Catch-up wage wording not adopted.
    slugs
    • mega-backdoor-roth

  7. What to do with after-tax 401(k) contributions ↗

    id
    money59-mega-backdoor-roth-fidelity-aftertax — What to do with after-tax 401(k) contributions
    platform
    Fidelity
    role
    Service rules
    accessed On
    2026-09-29
    published Or Updated
    2026-04-29
    locator
    Key takeaways; What you save; In-plan Roth conversion
    scope
    Three contribution categories and the treatment of unconverted earnings.
    limitations
    Provider explanation, not proof of employer eligibility. Promotional savings language omitted.
    slugs
    • mega-backdoor-roth

  8. Notice 2025-67: 2026 retirement-plan cost-of-living adjustments ↗

    id
    money59-mega-backdoor-roth-notice2026 — Notice 2025-67: 2026 retirement-plan cost-of-living adjustments
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-29
    locator
    PDF pages 1–2; sections 415(c), 402(g), 414(v)
    scope
    U.S. 2026 contribution ceilings and age-based catch-up amounts.
    limitations
    Annual adjustments, not employer permission or a 2027 announcement. Publication date not independently extracted.
    slugs
    • mega-backdoor-roth

  9. Fixing common plan mistakes: Failure to limit contributions for a participant ↗

    id
    money59-mega-backdoor-roth-additions — Fixing common plan mistakes: Failure to limit contributions for a participant
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-29
    locator
    Background; Annual additions; Finding the mistake
    scope
    Counted amounts, compensation ceiling and exclusions; arithmetic example uses separately verified 2026 dollars.
    limitations
    Displayed dollar list stops at 2024. Not used for a current dollar figure; correction-program deadlines not adopted.
    slugs
    • mega-backdoor-roth

  10. Rollovers of after-tax contributions in retirement plans ↗

    id
    money59-mega-backdoor-roth-aftertax-rollovers — Rollovers of after-tax contributions in retirement plans
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-29
    locator
    Rollovers to multiple destinations; principal-only question; earnings question; transition rules
    scope
    Allocation and split destinations under Notice 2014-54.
    limitations
    General distribution guidance, not a determination of which employer source accounts are available for withdrawal. No plan eligibility inference.
    slugs
    • mega-backdoor-roth

  11. Roth acct in your retirement plan ↗

    id
    money59-mega-backdoor-roth-roth-account — Roth acct in your retirement plan
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-29
    locator
    Designated Roth contributions; In-plan Roth rollovers
    scope
    Qualified workplace Roth distributions and relevant aging/qualifying-event conditions.
    limitations
    Workplace Roth rules; not a complete Roth IRA withdrawal guide or return forecast.
    slugs
    • mega-backdoor-roth

  12. Retirement plans FAQs on designated Roth accounts ↗

    id
    money59-mega-backdoor-roth-inplan — Retirement plans FAQs on designated Roth accounts
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-29
    locator
    Distributions; In-plan rollovers, especially eligible amounts, frequency, tax and recapture
    scope
    Tax/access cautions and permitted in-plan movement.
    limitations
    Fees are a checklist question, not an IRS fee schedule. Old annual-dollar examples not used. Workplace and IRA clocks must not be conflated.
    slugs
    • mega-backdoor-roth

  13. 401(k) plan Fix-it Guide: The plan failed the ADP and ACP nondiscrimination tests ↗

    id
    money59-mega-backdoor-roth-acp — 401(k) plan Fix-it Guide: The plan failed the ADP and ACP nondiscrimination tests
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-29
    locator
    Test descriptions and How to fix the mistake
    scope
    After-tax contributions in ACP testing and possible corrective distributions.
    limitations
    Only where testing applies. Historical HCE thresholds and correction deadlines not carried into the card; no assumption all safe-harbor contributions are exempt.
    slugs
    • mega-backdoor-roth

  14. Instructions for Form 8606 (2025) ↗

    id
    money59-mega-backdoor-roth-8606 — Instructions for Form 8606 (2025)
    platform
    Internal Revenue Service
    role
    Official context
    accessed On
    2026-09-29
    locator
    IRA definitions; Part I, lines 6–12; Part II
    scope
    IRA aggregation and proportional allocation for a separate IRA conversion.
    limitations
    Opened version explicitly says 2025. Used for the continuing allocation mechanism, not 2026 limits or assumed future tax-software menus.
    slugs
    • mega-backdoor-roth

  15. Mega Backdoor with Fidelity ↗

    id
    money59-mega-backdoor-roth-reddit-fidelity — Mega Backdoor with Fidelity
    platform
    Reddit · r/Bogleheads
    role
    Community discussion
    accessed On
    2026-09-29
    locator
    footpaste question; unbalancedcheckbook, circuitji, LnKAvenge, silverbug9 and call-friction replies
    scope
    Actual post/replies: automation, manual payday conversion, quarterly split, fund-mix question and call friction.
    limitations
    Original body opened directly this time, unlike prior archived inspection. Relative timestamps only; frozen metadata says 2024-01-18 but date not newly verified. Withdrawal replies are not tax authority.
    slugs
    • mega-backdoor-roth

  16. Mega Backdoor Conversion/Rollover Option ↗

    id
    money59-mega-backdoor-roth-reddit-fees — Mega Backdoor Conversion/Rollover Option
    platform
    Reddit · r/personalfinance
    role
    Community discussion
    accessed On
    2026-09-29
    locator
    Myantiscurious post and antoniosrevenge replies
    scope
    Reported $20 quarterly rollover fee versus free in-plan automation, fund choices and access discussion.
    limitations
    Historical individual report, not a verified current fee schedule. Exact publication date not exposed in opened body; no original date fabricated.
    slugs
    • mega-backdoor-roth

  17. Mega Backdoor Roth - When to roll into Roth? ↗

    id
    money59-mega-backdoor-roth-reddit-delay — Mega Backdoor Roth - When to roll into Roth?
    platform
    Reddit · r/Fire
    role
    Community discussion
    accessed On
    2026-09-29
    locator
    Magikarpical reply; route-difference replies in surrounding context
    scope
    Months of unconverted money, reported tax, later phone activation.
    limitations
    No exact tax amount or date independently verified. Do not adopt commenter’s personal contribution recommendation or imply every plan automates.
    slugs
    • mega-backdoor-roth

Keep this topic in view

Preserved original record

Earlier public profile and reader notes are preserved separately from the current article. They may contain superseded wording and are not newly checked material.

Read the full original profile
slug
mega-backdoor-roth
name
Mega backdoor Roth
aliases
  • after-tax 401k
  • mega backdoor
  • in-plan Roth conversion
  • after tax conversion
family
accounts
heat
high
talk
Lots of talk
most Discussed
false
first Line
A mega backdoor Roth is the informal name for moving after-tax workplace retirement-plan contributions into a Roth account when the plan allows the relevant steps.
why Line
The limiting factor is usually what the employer plan permits: after-tax contributions and a way to move them to Roth. A large headline ceiling is not the amount every employee can use.
feel Words
  • mega backdoor
  • after-tax 401k
  • in-plan conversion
  • roth conversion
common Picture
  • lead
    After-tax is different from a Roth salary deferral
    why
    The strategy uses a particular contribution feature and a permitted movement to Roth. [community]
  • lead
    2026 overall additions limit: $72,000
    why
    Counted employee and employer contributions share the ceiling; qualifying catch-ups are separate. [community]
  • lead
    Available room is the remainder
    why
    Plan restrictions and other contributions can reduce the after-tax amount available. [community]
watch For
Assuming every 401k has it. Hitting the IRS combined limit without doing the match first. Leaving after-tax sitting unconverted.
what People Say
  • The job: extra Roth room for people whose plan allows after-tax 401k. [community]
  • r/personalfinance and r/financialindependence treat this as the high-earner move once the match and regular Roth IRA backdoor are done. [community]
  • Bogleheads wiki is calmer than YouTube “secret 401k hack.” [community]
  • Why it is loud: the regular IRA backdoor caps at IRA limits. This can be much bigger if the plan cooperates. [community]
  • After-tax contributions alone are not the whole strategy: the plan also needs a permitted way to move the money to Roth. Earnings that accumulate before that step can have a different tax treatment from the already-taxed contribution. [community]
  • Administration matters: payroll categories, conversion records and the Form 1099-R need to agree. The plan administrator and a tax professional answer different parts of that question. This is not tax advice. [community]
  • Mega vs backdoor: backdoor Roth IRA is the IRA. Mega is 401k after-tax. People mix the names constantly. [community]
  • High earners hit the employee deferral cap and still have cash. That is the audience. [community]
  • If they cannot max the match and the employee deferral, this is not the next dollar. [community]
  • Fidelity / Vanguard plan PDFs are the source, not a TikTok. [community]
  • Mega is optional. Plenty of good years never touch it. [community]
how People Run It
  • Read the Summary Plan Description or ask the administrator: does it permit after-tax contributions, conversion to Roth within the plan, or a permitted rollover while still employed? These are separate features. [community]
  • Do the match and pre-tax/Roth deferral first. [community]
  • Set after-tax contributions if the doors are open. [community]
  • Convert after-tax to Roth often (some do it every paycheck) so earnings in after-tax stay small. [community]
  • They track the IRS annual additions limit so they do not bounce contributions. [community]
  • They keep a spreadsheet of after-tax vs Roth vs pre-tax buckets. [community]
  • If the plan cannot convert, they stop or they wait for a rollover event — they do not invent a door. [community]
amounts People Use
  • Employee deferral cap still exists (the numbered IRS limit that year). [community]
  • After-tax is extra up toward the overall 401k additions limit (a higher IRS number that includes employer). [community]
  • Convert: as soon as the plan allows, often each paycheck or monthly. [community]
  • IRA backdoor is still the IRA contribution limit — different pile. [community]
  • $0 if the plan does not allow it. [community]
how People Keep It
  • A calendar reminder to convert if it is not automatic. [community]
  • They do not pause the match to fund after-tax. [community]
  • Emergency fund still exists. This is extra, not rent. [community]
  • They re-read the plan after a job change. [community]
  • A tax person in a year they converted a lot. [community]
how It Feels
  • First plan-document read: ordinary pre-tax deferrals, Roth deferrals and separate after-tax contributions can look similar until their tax treatment and limits are set out separately. [community]
  • First conversion: they wait for the 1099 like it is a trap. Often it is just paperwork. [community]
  • If they left after-tax unconverted for a year: taxable earnings. Annoyance, not doom, in most logs. [community]
  • If the plan said no: they use taxable brokerage / backdoor IRA and stop hunting a hack. [community]
  • High cash year: this feels like a cheat code. It is just a plan feature. [community]
  • Changing jobs: employees have to review the new employer’s plan document because the same features may not be available. [community]
how Long People Run It
  • While the plan allows it and cash is extra. [community]
  • Stops at a job without the feature. [community]
  • Not a personality. [community]
  • They re-check every open enrollment. [community]
deep Dive
  • Regular IRA backdoor versus mega backdoor: the former uses a nondeductible IRA contribution and conversion. The latter starts with a workplace plan’s separate after-tax contribution feature; it is not simply a larger IRA contribution. [community]
  • Employer matching remains a separate feature: the match follows the plan’s formula for qualifying employee contributions. Available after-tax room is calculated after relevant other employee and employer additions. [community]
  • If the plan lacks the feature: a taxable brokerage is one separate investing option discussed. It does not reproduce the Roth tax treatment; the comparison concerns flexibility, tax and the purpose of the money. [community]
  • Roth salary deferrals are not the same contribution type: Roth-versus-Traditional usually compares the employee’s ordinary retirement deferrals. A mega backdoor relies on a separate after-tax contribution source and a permitted movement to Roth. [community]
  • Do not copy the IRA calculation by name alone: an IRA backdoor and a workplace-plan conversion have different account histories and allocation rules. After-tax principal and untaxed earnings need to be identified in the actual transaction. This is not tax advice. [community]
watch For Long
  • No after-tax source in the plan = no mega. [community]
  • Skipping the match to “max mega.” [community]
  • Letting after-tax sit unconverted. [community]
  • YouTube dollar amounts that ignore this year’s IRS limits. [community]
  • This is not tax advice and not a promise of tax-free anything. [community]
related
  • backdoor-roth
  • the-match
  • roth-vs-traditional
  • taxable-brokerage
  • four-oh-one-k-rollover
research Pointer
    house Pointers
      play Pointer
      —
      sources
      • r/personalfinance mega-backdoor threads
      • Bogleheads after-tax 401k wiki talk
      • plan SPD examples in FI rooms
      disclaimer
      Community talk may be wrong. Not financial, tax, legal, or investment advice. No return or outcome is promised.
      quick Answer History
      • field
        commonPicture
        rows
        • lead
          Plan must allow after-tax
          why
          If the SPD does not say so, this card is a no. [community]
        • lead
          One combined 401k limit
          why
          Employee + after-tax + employer share a ceiling. [community]
      • field
        communityPicture
        rows
        • People discuss the difference between after-tax and Roth contributions, available conversion or rollover features, and plan-specific administration.
      • field
        firstLine
        rows
        • Mega backdoor Roth is after-tax 401k money converted to Roth — not the regular backdoor IRA.
      • field
        whyLine
        rows
        • Mega backdoor Roth is after-tax 401k money converted to Roth — not the regular backdoor IRA.
      • field
        commonPicture
        rows
        • lead
          Plan must allow after-tax contributions and a Roth conversion route
          why
          The summary plan description, often called the SPD, lists the available features. [community]
        • lead
          Convert soon
          why
          After-tax → Roth so growth is Roth. [community]
        • lead
          Match still first
          why
          Free money before extra after-tax. [community]
        • lead
          2026 overall 401(k) additions limit: $72,000
          why
          Employee, employer and after-tax contributions share this limit; qualifying age catch-ups are separate. [community]
        • lead
          Not the IRA backdoor
          why
          That is a different card. [community]
        • lead
          Available after-tax room is what remains under that limit
          why
          Subtract the counted employee and employer contributions; the plan can impose additional restrictions. [community]
      • field
        whatPeopleSay
        rows
        • Why it fails: the plan has after-tax but no conversion path, so money sits taxable-growth-awkward. [community]
        • Not tax advice. Payroll, pro-rata, and the Form 1099-R are a person and a tax person. [community]
      • field
        howPeopleRunIt
        rows
        • Read the plan SPD / call HR: after-tax allowed? in-plan Roth conversion or in-service rollover? [community]
      • field
        howItFeels
        rows
        • First SPD read: confused. After-tax vs Roth vs pre-tax is three words that look the same. [community]
        • Job hop: they have to learn a new SPD from zero. [community]
      • field
        deepDive
        rows
        • Backdoor Roth (IRA) is the sibling card. Start there if they do not even have an IRA Roth door. [community]
        • The match is still the first 401k dollar. [community]
        • Taxable brokerage is what people use when mega is impossible. [community]
        • Roth vs Traditional is the split inside the employee deferral, not this after-tax door. [community]
        • Pro-rata IRA rules are the regular backdoor headache; mega lives in the 401k. Still not advice. [community]
      Read the preserved reader notes
      definition
      A mega backdoor Roth is the informal name for moving after-tax workplace retirement-plan contributions into a Roth account when the plan allows the relevant steps.
      community Picture
      The limiting factor is usually what the employer plan permits: after-tax contributions and a way to move them to Roth. A large headline ceiling is not the amount every employee can use.
      additions
      summary Sources
      guide
      what
      • Mega backdoor Roth is informal language for after-tax contributions inside a workplace retirement plan, followed by a conversion to Roth inside the plan or a rollover out, when the plan allows those exact steps. It is not the IRA backdoor, and it is not the regular Roth deferral elected on the paycheck.
      • After-tax employee contributions, Roth deferrals, and pre-tax deferrals are different buckets. The IRS newsroom's $24,500 employee deferral for 2026 is the elective-deferral figure. The overall annual-additions limit, which is what makes extra after-tax room possible, is in Notice 2025-67, not in a forum's memory of last year's number.
      • A plan can allow after-tax contributions and still not allow an in-plan Roth conversion or an in-service rollover. Those are separate features. Without the conversion or rollover path, after-tax money can sit with later earnings that are not Roth.
      how
      • Read the summary plan description or ask the administrator three yes-or-no questions: after-tax contributions, in-plan Roth conversion, and in-service rollover of after-tax money. Write the answers down. A coworker’s plan is not this plan.
      • Take the match and decide the pre-tax or Roth elective deferral first. The match formula can require a deferral type and a percentage. Filling the plan with after-tax money and missing the match is a bad trade if the match was available.
      • If the doors are open, set the after-tax amount the payroll system actually supports, and turn on the conversion the plan offers so the after-tax contribution does not linger. Watch the annual-additions limit in the current IRS notice so employee and employer money together do not exceed it.
      • If any answer is no, stop. There is no mega backdoor at that employer until the document changes. Do not send after-tax money into a plan that cannot convert it and then hope.
      understand
      • The room exists only because workplace plans can accept after-tax contributions up to a higher overall limit than the elective deferral, and only some plans then allow those dollars to become Roth. The nickname makes it sound like a right. It is a pair of plan features.
      • The miss is assuming every 401(k) has it, leaving after-tax contributions unconverted, or hitting the overall limit and crowding out the match. Another miss is using last year's annual-additions number after the IRS has published a new notice.
      • Community notes trade administrator scripts and custodian menus. The SPD is the permission. Notice 2025-67 is the year's dollar limit.
      sources
      note References
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      End of Mega backdoor Roth