The mega backdoor Roth IRA is a strategy ‘highly compensated employees’ or HCEs at Paccar can use to increase retirement savings and shelter investment growth from taxes in retirement.

When circumstances are right and the stars align, this little-known strategy can be a smart way to tuck extra money into a Roth IRA to use for retirement or to save for your heirs.

Let’s start with the basics.

Retirement Savings 101

When you choose to make Roth contributions, you’ll contribute to your account with after-tax dollars. This means you will pay taxes on the money the year it is earned, and you won’t benefit from any tax advantages at the time you contribute.

In exchange, you won’t owe any taxes on your contributions or when you withdraw in the future. Additionally, as long as your Roth contributions have “aged” for at least five years, any earnings your contributions accrue won’t be taxed either. (That said, if Paccar made any contributions, you’ll still need to pay taxes on those when you withdraw, since you won’t have paid taxes on those contributions yet. Contributions made by Paccar are always traditional, pre-tax contributions.) 

The 2026 limits have changed since last year. A person younger than 50 can contribute $20,500 into their 401(k). People who are aged 50 and older can contribute an additional $6,500 annually in catch-up contributions, for a total of $27,000 into their 401(k). Limits for total employee and employer contributions have also increased over the past year and are $61,000 (or $67,600 for people 50 and older).

Some company 401(k) plans are structured to allow for additional after-tax contributions, which can create a “mega backdoor” through which you can invest up to an extra $40,500 into your Roth IRA or Roth 401(k).

We’ll walk you through how it works and if it’s a good move for you, but know now that this is complicated and advanced financial planning with the potential for some unexpected tax bills—definitely work with an expert on this one.

Is a Mega Backdoor Roth Possible ?

There are two prerequisites — if you’re unsure about either, double-check with HR or contact your Paccar-plan administrator.

1. Your 401(k) plan must allow for after-tax contributions. Not all 401(k) plans let you make after-tax contributions. Quick vocab lesson: after-tax is an entirely different contribution category from pre-tax and post-tax. (We’ve mentioned before how after-tax and post-tax used to be conflated.)
2. Your 401(k) plan must also allow for in-service withdrawals or in-plan Roth conversions. In-service withdrawals (also called in-service distributions) enable you to take money out of your 401(k) while you’re still employed with Paccar and roll it into a Roth IRA. In-plan conversions let you move your after-tax contribution into Roth dollars within the 401(k).

Mega Backdoor Roth IRA Pros

• Due to the dollar amounts, this strategy can really move the needle in your overall retirement savings and tax-free Roth asset bucket. Even if Paccar only permits this for a few years, it can still be worthwhile, assuming it makes sense in the context of the rest of your financial situation
• If you can keep the entire mega backdoor Roth strategy in-plan, it can be fairly easy to execute for the individual.

Mega Backdoor Roth IRA Cons

• Most individuals don’t have the flexibility to maximize the benefits of this strategy, especially on an after-tax basis.
• Even when individuals have the means to use this strategy, it might not work at the plan level. Essentially, your Paccar-sponsored 401(k) plan must pass various testing requirements. This includes participation from ‘highly compensated employees’ or HCEs relative to ‘non-highly compensated employees’ or NHCEs. If only the  HCEs are making after-tax contributions  (as stands to reason), the plan may be forced to return a portion of the contributions to HCE participants if it fails the test.

How a Mega Backdoor Roth Works

The  real  limit on a contribution plan such as a 401(k) is actually pretty high: this year, it’s $61,000 (or $67,500 for people 50 and older). That max amount includes the $20,500 (or $27,000) employee elective deferral amount we’re most familiar with,  as well as  any matching contributions from Paccar, profit-sharing, and your after-tax contributions.

Military families balancing service-connected benefits with employer plans should take a close look at what Paccar provides. According to publicly available information, Paccar maintains an active defined benefit pension plan, which provides retirement income based on factors such as years of service and compensation history. Paccar does not appear to offer a formal retiree healthcare program, making healthcare coverage planning an important consideration if you retire before age 65. Because the specifics of your pension formula, vesting schedule, and benefit eligibility depend on your individual employment history and plan documents, We encourage you to review your Summary Plan Description (SPD) or speak with Paccar's HR or benefits team for the most current details.

When you use the mega backdoor strategy, you take all the money from the after-tax contribution to your 401(k) and quickly transfer it into either a Roth IRA or to Roth dollars within your 401(k) before it can accrue investment earnings. There are also some instances where a company’s highest earners wouldn’t be able to max out their after-tax contributions due to  IRS nondiscrimination tests .  If available once it’s in a Roth-style account, the money will grow tax- free  instead of tax- deferred , which means you won’t end up owing taxes on those earnings, and neither will your beneficiaries. Pretty nifty.

Speed is key, which is why in-service withdrawals or in-plan conversions is one of the requirements.  You don’t want to have to wait until you leave Paccar to move that chunk of money. 

NOTE: If you leave it as an after-tax contribution in your 401(k), it’s going to be accruing taxable earnings the whole time. 

Doing the process manually is complicated, and we are here to assist.

Say you miss an in-service withdrawal or in-plan conversion and you’ve accrued some earnings. Not the end of the world. The IRS  confirms  you can shift the contribution portion into a Roth IRA and the gains portion into a traditional IRA, which takes some work, but you’ll preserve your contribution’s beneficial tax status.

Calculate Your After-Tax Contribution Amount

You’ll notice that we keep saying “up to $40,500” in additional contributions—that’s because everyone’s after-tax amount could be different. If you’re trying to make up the difference between the $20,500/$27,000 standard employee contribution amount and the $61,000/$67,500 max limit, you have to account for any matching by Paccar and profit-sharing along the way.

Let’s walk through a couple of simple scenarios.

Henry, 57

Max limit, based on age: $67,500

Salary: $100,000

Profit-sharing: 25 percent of salary

At 56, Henry has higher limits. If he maxes out his $27,000 employee contribution and gets $25,000 from his employer, Henry has room for $15,500 in after-tax contributions.

Nancy, 44

Max limit, based on age: $61,000

Salary: $100,000

Employee matching: Up to 3 percent of salary

If Nancy maxes out the $20,500 employee contribution, and her company matches $3,000, that means Nancy has room for $37,500 in after-tax contributions.

Jason (60 years old)

Max limit, based on age: $67,500

Contributes the maximum annual amount to both his 401(k) ($27,000 in 2026) and his IRA ($7,500 in 2026). He is looking to save even more by using a mega backdoor Roth IRA contribution, but he wants to know the maximum amount of after-tax contributions he can put into his 401(k) plan. If his total annual employer matching contributions are $10,000 in 2026, Jason can make after-tax contributions of up to $30,500 this year. Assuming his 401(k) plan has the appropriate provisions, John would transfer his after-tax contributions to his Roth 401(k) or Roth IRA, allowing him to place an additional $30,500 in a Roth account receiving tax-free growth.

One caveat: Some 401(k) plans do limit the amount you can contribute after-tax, so even if you have room to contribute more, you might not be able to. There are also some instances where a company’s highest earners wouldn’t be able to max out their after-tax contributions due to  IRS nondiscrimination tests , which are designed to ensure those earning the most aren’t saving at a higher rate than everyone else in their organization.

And it bears repeating after-tax contributions aren’t deductible, and if left in the 401(k) plan instead of being shifted into a Roth-style account, the earnings could be taxed when withdrawn.

When you should consider a mega backdoor Roth

Mega backdoor Roths are an interesting option for high earners at Paccar looking for additional ways to save for retirement or for their heirs. It’s worth exploring with your financial planner if:

• You’ve maxed out your personal 401(k) contributions. That comes first. When you’ve maxed out your contributions and still have more to save, you can consider going for a mega backdoor strategy.
• You have additional funds you want to save for retirement. Mega backdoor Roths are a great way to store away cash every year. Still, there are many other financial strategies to consider, and things like time horizon and liquidity are important considerations.