Understanding The Mega Backdoor Roth IRA

Mega Backdoor Roth IRA

There has been a lot of talk lately about the mega backdoor Roth IRA. For a long time, it was an unspoken secret used by retirement planners. However, the IRS released guidance that specifically addressed both backdoor Roth IRA conversions, and the so-called Mega Backdoor Roth IRA. As a result, it has gained even more popularity and interest.

So what is the Mega Backdoor Roth IRA? The Mega Backdoor Roth IRA allows you to contribute an additional $35,000 into an Roth IRA by leveraging the fact that some employer 401k plans allow after-tax contributions up to the current limit of $53,000. 

Wait, what? I thought the Roth contribution limit in 2018 is $5,500 (and $6,500 if you’re over 50). How can you contribute over 6x that amount?

Let’s dive into a little background, and then show how the process works.

Quick Navigation

First: Why A Roth vs. Traditional vs. 401k
Background: A Regular Backdoor Roth IRA Conversion
How The Mega Backdoor Roth IRA Works
A Step By Step Process For Doing A Mega Backdoor Roth IRA Conversion

First: Why A Roth vs. Traditional vs. 401k

​I think it’s important to first have a discussion on why this even matters. Because, for some people, it doesn’t matter.

Who This Article Doesn’t Apply To:

  • If you don’t max out your 401k contributions and your IRA contributions currently (this means putting in $18,500 pre-tax to your 401k, and $5,500 to your IRA)
  • If you don’t meet the income limitations to have a deductible IRA (if you can deduct your IRA contributions, do that)
  • If your employer doesn’t offer after-tax 401k contributions (you might still want to read this and be in the know, but it won’t help you and I’m sorry your employer sucks)

Why Bother With A Roth vs. A Traditional IRA vs. A 401k

Without dragging on a long conversation here, we have an amazing article on when to contribute to a Roth IRA vs. a Traditional IRA. It’s a long one, but it goes into detail about the tax consequences of each. I highly recommend you leverage that article as a basis for this. 

But honestly, tax diversification is one of the biggest reasons to consider this strategy. It can be benefit to be able to take advantage of both taxable and tax-free accounts in retirement. It *might* also be a benefit to pay any potential taxes today to enjoy tax-free retirement later. It really depends on your tax situation, but if you’re already reading this far, you likely know that already.

Background: A Regular Backdoor Roth IRA Conversion

The Backdoor Roth IRA Conversion is an indirect way to contribute to a Roth IRA when you are not eligible to contribute directly due to high income.

Remember, to be able to fully contribute to a Roth IRA, you have to meet the following income limits (as of 2018):

Roth IRA Contribution Income Limits 2018

Single Filers

Married Filing Jointly

Phase Out Starts



Ineligible To Contribute



If you make more than the income limits, and have earned income, you can still contribute to a non-deductible traditional IRA. The Backdoor Roth IRA uses this tactic to then convert the non-deductible traditional IRA contribution into a Roth account. 

Here’s briefly how it works in three steps.

Step 1 – Ensure You Don’t Have Any Other Pre-Tax IRA Accounts

​To avoid many complexities and potential problems, you should eliminate any traditional IRAs, SEP IRAs, or SIMPLE IRAs, unless you are looking to convert those into Roth IRAs. You can eliminate them by rolling them over into an employer sponsored plan, such as a 401k, 403, or 457. This is called a reverse IRA to 401k rollover. You will then be leveraging this employer sponsored plan for the Mega Backdoor Roth IRA.

Remember, you can also only rollover pre-tax money, so any previous non-deductible contributions are not eligible for this.

Step 2 – Make A Non-Deductible IRA Contribution

​Once you’ve eliminated all your traditional IRA accounts, it’s time to actually start contributing to your Backdoor Roth IRA. This is the easy part. 

Simply open a Traditional IRA Account and a Roth IRA Account at the same firm (you might already have this). Then, contribute $5,500 (the 2018 limit) as a non-deductible contribution to your Traditional IRA.

Step 3 – Convert The Traditional IRA To The Roth IRA

This step is also pretty easy, but there are some caveats. ​First, you should wait at least one day after the money clears the deposit into your Traditional IRA before converting it. The IRA has no guidelines on this, but it’s good to show a clear step-by-step process of how you converted. 

For many online brokerage​ firms make this step pretty easy, but it can be scary. At most firms, you simply transfer the balance from the Traditional IRA to the Roth IRA. That’s it. Others might make you sign a form. Almost all will warn you about the tax implications of this, which is the “scary” part of the transaction.

We’re fans of TD Ameritrade as our brokerage because they offer no-fee IRAs, and have over 100 commission free ETFs (including popular Vanguard ETFs). ​Open a TD Ameritrade account here for free.

We’re not tax experts, but here’s a great guide on how to report the taxes on your backdoor Roth IRA.​

How The Mega Backdoor Roth IRA Works

Okay, now that you’ve had the refresher on the Backdoor Roth IRA, how does the Mega Backdoor Roth IRA work? Well, it takes advantage of the fact the after-tax contributions to a 401k plan are treated just like a Traditional IRA in the above example of the Backdoor Roth. 

It honestly just adds one more step to the process. But it requires that you have an employer 401k that allows after-tax contributions. We’re not talking Roth contributions, but after-tax contributions.

A note on after-tax 401k contributions. Remember, the IRS limits on total 401k contributions is $55,000 in 2018. That means that you can contribute $18,500 pre-tax, and your employer typically contributes something. Some 401k plans then allow employees to contribute the remaining amount in after-tax contributions.

For example, let’s say your employer matches you $6,000 into your 401k. You can contribute $18,500 pre-tax, your employer puts in $6,000, and that leaves you $28,500 that you can potentially contribute after-tax if your employer allows it.

Your 401k Plan Must Meet Specific Criteria To Do A Mega Backdoor Roth IRA

In order to do a Mega Backdoor Roth IRA, your 401k plan needs to offer:

  • After-Tax Contributions Above and Beyond the $18,500 Pre-Tax Contribution Limits
  • In Service Distributions Or Non-Hardship Withdrawals 

If your 401k plan doesn’t offer non-hardship in service withdrawals, you might still be able to accomplish the same thing if you’re leaving your company soon. 

And there is also thoughts that even if you can’t do in-service withdrawals, it still might be very worthwhile.​

You can then max out your 401k with after-tax contributions up to the contribution limit each year. You can then withdraw that money into a Traditional IRA, and do the same process as a Backdoor Roth IRA.​

A Step By Step Process For Doing A Mega Backdoor Roth IRA Conversion

The process for doing a Mega Backdoor Roth IRA Conversion is essentially the same as the Backdoor Roth IRA Conversion, with just two additional steps.​

Mega Step 1 – ​Maximize Your After-Tax 401k Contributions

The first additional step for the Mega Backdoor Roth IRA is that you need to figure out how much to contribute to maximize your after-tax 401k contributions.

This means understanding your employer’s plan, and then making the additional contributions. This can be a challenge because many plans require you to specify a percentage of your paycheck, versus a set amount. You also want to make sure that these contributions are AFTER-TAX, NOT Roth 401k contributions. ​

Mega Step 2 – Withdraw The After-Tax Portion To A Traditional IRA

​Once you’ve maxed out your after-tax contribution, you can withdraw that portion to a Traditional IRA if your employer allows in-service non-hardship withdrawals. Otherwise you need to wait until termination, and you can rollover the after-tax portion into a Traditional IRA.

Once the funds are in the Traditional IRA, the process works the same as the Backdoor Roth IRA Conversion. You just have a lot more money to work with beyond the typical $5,500 annual contribution.​


The Mega Backdoor Roth IRA is another potential tool to maximize tax savings IF you have more bandwidth for savings. This strategy is really for people who are maximizing their savings in other avenues first: 401k, IRA, HSAs, 529s.

If you still need or want more tax sheltered savings, then this is potentially a great strategy if your employer allows it.

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Author: Robert Farrington