{ "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", "mostDiscussed": false, "firstLine": "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.", "whyLine": "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.", "feelWords": [ "mega backdoor", "after-tax 401k", "in-plan conversion", "roth conversion" ], "commonPicture": [ { "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]" } ], "watchFor": "Assuming every 401k has it. Hitting the IRS combined limit without doing the match first. Leaving after-tax sitting unconverted.", "whatPeopleSay": [ "**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]" ], "howPeopleRunIt": [ "**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]" ], "amountsPeopleUse": [ "**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]" ], "howPeopleKeepIt": [ "**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]" ], "howItFeels": [ "**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]" ], "howLongPeopleRunIt": [ "**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]" ], "deepDive": [ "**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]" ], "watchForLong": [ "**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" ], "researchPointer": [], "housePointers": [], "playPointer": null, "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.", "quickAnswerHistory": [ { "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]" ] } ] }