Mega Backdoor Roth Plan-Fit and Setup Checklist
Test plan fit, add two required features, and automate Roth conversions
- Difficulty
- Moderate
- Time to result
- ~weeks to results
- Steps
- 5
- Confidence
- 94%
Start by testing whether meaningful demand exists among employees who already maximize ordinary 401(k) contributions. The employer and provider then model whether after-tax contributions can pass the additional compliance testing, particularly when highly compensated employees would dominate participation. If the plan is viable, amend it to support the two essential components: after-tax employee contributions and a mechanism that moves those dollars into Roth status. That mechanism can be an in-plan Roth conversion or an in-service distribution to a Roth IRA. Finally, minimize manual work and taxable growth by enabling an automatic Roth conversion or sweep when the record keeper supports it, and verify the first transaction directly with the provider.
Origin
Extracted from Masters in Business, in an At The Money discussion with retirement-plan specialist Dan L. Rosa.
Core principles
- 01Confirm participant demand before changing the plan
- 02Treat compliance testing as a plan-design constraint
- 03Enable both after-tax contributions and a Roth transfer mechanism
- 04Convert after-tax contributions promptly to limit taxable growth
- 05Prefer automation over recurring manual paperwork
How to run it
- 1
Measure employee demand
Identify employees who already maximize regular contributions and would contribute more if permitted. Strong broad-based demand is the first indication that the feature deserves evaluation.
Pro tip Use current contribution data rather than relying only on an informal survey.
Watch out Interest limited to owners and the highest earners can make the design fail compliance testing.
- 2
Model compliance viability
Have the employer and 401(k) provider test how after-tax contributions affect the plan. Evaluate the number and concentration of highly compensated participants before amending documents.
Pro tip Model several participation levels so the employer understands how changing enrollment could affect the result.
Watch out A failed additional compliance test can prevent the strategy from working altogether.
- 3
Enable after-tax contributions
Amend the plan documents so participants can contribute after-tax dollars above the ordinary elective-deferral limit, subject to the overall plan limit.
Pro tip Ask the provider to distinguish clearly between Roth elective deferrals and after-tax contributions.
Watch out After-tax contributions alone do not complete the strategy.
- 4
Add a Roth transfer path
Provide either an in-plan Roth conversion that keeps the assets in the 401(k), or an in-service distribution that moves them to an outside Roth IRA.
Pro tip Use an in-plan conversion when administrative simplicity and keeping assets inside the plan are priorities.
Watch out Confirm the tax treatment of any earnings accumulated before conversion.
- 5
Automate and verify conversions
Activate a daily automatic Roth conversion when the provider offers it. If conversions are manual or limited, establish a recurring process and confirm the first transaction with the provider.
Pro tip Convert promptly to reduce the time during which after-tax contributions can generate taxable earnings.
Watch out The employee may need to activate the automatic conversion even after the employer enables it.
In the wild
A 100-person advisory firm finds that many employees already maximize regular 401(k) contributions and that interest extends beyond its owners. The employer asks its provider to model compliance, amends the plan to allow after-tax contributions and in-plan Roth conversions, and invites eligible employees to activate automatic sweeps.
→ The firm adds a viable savings option without relying on recurring manual conversion forms.
An employee confirms that the plan supports after-tax contributions but discovers that automatic Roth conversion is not enabled by default. The employee contacts the provider, activates the feature, verifies the first conversion, and then monitors subsequent statements.
→ Future after-tax contributions move promptly into Roth status with less administrative effort.
Common mistakes
Confusing Roth deferrals with after-tax contributions
A Roth 401(k) election uses the ordinary elective-deferral limit; the mega backdoor strategy requires a separate after-tax contribution source.
Ignoring plan-level compliance testing
Employer enthusiasm is insufficient if participation patterns make the additional testing fail.
Leaving conversions entirely manual
Infrequent manual conversions add administrative burden and allow earnings to accumulate before Roth conversion.
Is it for you?
Best for
It is best for employers with substantial high-earner participation and employees who can save beyond ordinary 401(k) limits.
Not ideal for
It is not ideal for plans where only owners or a small top-heavy group would make after-tax contributions, unless the plan covers owners only.
From the transcript
“For the megabackdoor ROTH to work. A plan has to allow two things.”
“The first is the ability to make after tax contributions and the second is a way to move those after tax dollars into.”
“Others have daily automatic roth conversions, which is just awesome.”
From the episode
At The Money: The Mega Backdoor Roth