I have a question for you: What is your favorite tax rate? This is not intended as a trick question. If you’re like most people, your favorite tax rate is probably zero.

While a 0% rate is great, however, it’s not easy to achieve. There is really just a handful of ways to create tax-free income. If you are early in your career and have young children, 529 accounts are a great option. Or, if you are later in your career, you can invest in tax-exempt municipal bonds. And then there are Roth IRAs, which, in my opinion, are the best, most flexible and most effective tool to generate tax-free income when you reach retirement.

As with all good things, though, the IRS limits taxpayers’ ability to use Roth accounts. Each of the three primary ways to fund a Roth carries limitations: If you want to contribute directly to a Roth IRA, there are income thresholds: Individuals earning more than $135,000 and couples earning more than $199,000 are ineligible to contribute to Roth IRAs. And, though there is a way to work around these income limits, contributions are still limited: This year the limit is $5,500 per person ($6,500 if you are 50 or older). If you have a Roth 401(k) option at work, that’s great, but this feature isn’t universally available. And, if you go that route, you lose the valuable tax deduction associated with traditional 401(k) contributions. Finally, if you want to fund a Roth IRA via a Roth conversion, that entails a difficult decision to accelerate payment of a potentially large tax bill.

The result is that many people look at Roth accounts — with their zero tax rate on withdrawals — as a sort of promised land, but they have a hard time making significant contributions. That’s why I’d like to introduce you to one more method — one that isn’t widely discussed — to potentially make larger Roth contributions. The technique involves making after-tax contributions to your 401(k). This is how it works:

Step 1: Contact your employer and ask whether your plan will permit after-tax contributions in excess of the $18,500 pre-tax limit. If so, ask for information on how to set it up.

Step 2: Decide how much you want to contribute from each paycheck. In general, the total amount that can go into your 401(k), including both employee and employer contributions, is $55,000 per year. Even if your employer offers a generous match, that may still allow quite a bit of headroom to make an additional contribution before hitting that ceiling. Suppose, for example, that you make the maximum contribution of $18,500 and that your employer’s match adds another $10,000. That would bring the total contribution to $28,500, allowing you to contribute as much as another $26,500 (assuming you have the funds available) on an after-tax basis.

Step 3: When you retire or leave your employer, you’ll request two separate rollover checks. One will go to your traditional IRA, like an ordinary 401(k) rollover. The other check can go into your Roth IRA. (Note: Only your accumulated after-tax contributions can go into your Roth; all of the earnings must go into your traditional IRA.)

If your retirement plan administrator permits it, I believe this approach would allow you to contribute far more to a Roth IRA than you could using any other method (though it’s important to note that there is no trade off; even if you’re making direct Roth IRA contributions, you can still take advantage of this strategy to further increase your Roth contributions.)

Since this strategy is relatively new, I recommend the following “belt and suspenders” steps to ensure that it goes smoothly:

1. Be sure to consult your accountant in advance. The IRS approved this strategy only recently, so you want to be sure your CPA is aware of what you are doing and agrees that it makes sense in the overall context of your tax picture. (If your accountant is not familiar with it, you can refer them to IRS Notice 2014-54, “Guidance on Allocation of After-Tax Amounts to Rollovers.”)

2. Keep good records. When you employ this technique, your after-tax contributions will be mixed in with your standard pre-tax contributions. Your plan administrator will be responsible for tracking them separately, but it doesn’t hurt to maintain your own records.

3. When you retire or leave your employer, speak with your plan administrator well in advance of initiating a rollover. Remind them that your balance includes both pre-tax and after-tax contributions to ensure that they correctly issue two checks. And, at the beginning of the following year, be sure you receive two separate 1099-R forms, one for each rollover.