What Is a Nondeductible IRA? Explained Simply

Most people have heard of two flavors of IRA. There is the traditional IRA, where you often get a tax deduction now and pay tax later. And there is the Roth IRA, where you pay tax now and pull out money tax-free later. So where does a nondeductible IRA fit in? The short answer is that it is not a third kind of account at all. It is a traditional IRA that happens to hold money you did not get to deduct.

That sounds like a raw deal at first. Why put money into a traditional IRA and skip the deduction, the very thing that makes it attractive? It turns out there are good reasons, and for higher earners a nondeductible contribution can be the first step toward getting money into a Roth. This guide walks through the why, the how, and the two traps that trip people up the most. We will keep the math simple and honest, and we will point you to the exact IRS forms that make it all official.

What a nondeductible IRA actually is

Picture a single traditional IRA account. Over the years, some of the money you put in may have been deducted on your tax return. Some of it may not have been. The dollars you did not deduct are called your basis, or your after-tax money. The dollars you did deduct, plus all the investment growth, are your pretax money.

A nondeductible IRA is simply a traditional IRA that contains some of that after-tax basis. You do not check a special box at the bank or open an account with a different name. You make a normal traditional IRA contribution, you decide not to deduct it, and then you report that choice to the IRS on a form called Form 8606. That form is the record keeper. It tells the government, and future you, how much of the account you already paid tax on.

Why does the label matter so much? Because when the money eventually comes out, the IRS needs to know which dollars were already taxed and which were not. The after-tax basis comes back to you tax-free. The rest is taxed as ordinary income. Without a clean record, you risk paying tax on money you already paid tax on once before. That is the whole reason nondeductible contributions get their own paperwork.

Why people contribute after-tax dollars in the first place

Nobody wakes up wanting to skip a tax deduction. People end up making nondeductible contributions because a rule closes a more attractive door. There are two main situations.

Reason one: your income is too high to deduct a traditional contribution

If you or your spouse are covered by a workplace retirement plan, like a 401k, the IRS limits how much of a traditional IRA contribution you can deduct once your income climbs high enough. Above a certain income, the deduction disappears entirely. You are still allowed to contribute to the IRA. You just cannot write it off. That contribution becomes a nondeductible one, and the money still grows tax-deferred inside the account.

Reason two: your income is too high to fund a Roth directly

A Roth IRA has its own income ceiling. Earn above it and you cannot contribute to a Roth the normal way. But there is no income ceiling on making a nondeductible contribution to a traditional IRA. That is the seed of the so-called backdoor Roth, which we cover in detail below. A high earner puts after-tax money into a traditional IRA, then converts it to a Roth. The nondeductible contribution is the entry point.

In both cases, the person is not choosing to give up a deduction for fun. They are working around an income limit that blocked the choice they really wanted. A nondeductible IRA is the fallback that keeps their options open.

How the deduction phaseout works

The deduction for a traditional IRA does not vanish all at once. It fades out across a band of income called a phaseout range. Below the range, you can deduct the full contribution. Inside the range, you can deduct part of it. Above the range, you can deduct none of it, and any contribution you still make is nondeductible.

The exact dollar figures for the phaseout range are set by the IRS and adjust most years for inflation. They also depend on your tax filing status and on whether you, your spouse, or neither of you is covered by a workplace plan. Because these numbers move, the safest habit is to check the current IRA deduction limits page on IRS.gov for the year you are filing, rather than relying on a figure you remember from a few years ago.

The mechanics, though, stay the same. Here is a labeled example to show the shape of it. Imagine a single filer who is covered by a 401k at work, and imagine the phaseout range for that year runs from 80,000 dollars to 90,000 dollars of income. That is a 10,000 dollar wide band.

• Income of 75,000 dollars sits below the band. The full contribution is deductible.
• Income of 85,000 dollars sits at the midpoint. Roughly half of the contribution is deductible and half is nondeductible.
• Income of 95,000 dollars sits above the band. None of the contribution is deductible, so the whole thing is nondeductible.

Those 80,000 and 90,000 figures are just a stand-in to show the pattern. Always confirm the real range for your year and filing status. The key idea is that a phaseout is a slope, not a cliff. As your income rises through the band, the deductible slice shrinks and the nondeductible slice grows.

The 2026 contribution limit still applies

Whether your contribution is deductible or not, the annual IRA contribution limit is the same. For 2026, that limit is 7,500 dollars if you are under 50. Savers age 50 and older can add a catch-up amount on top, which raises the total they can put in for the year. Check the current retirement topics page on IRS.gov for the exact catch-up figure that applies to you.

A few things about this limit are worth pinning down. First, the limit is shared across all your IRAs combined. You cannot put 7,500 dollars into a traditional IRA and another 7,500 into a Roth in the same year. The cap covers both together. Second, you need enough earned income to support the contribution. And third, deductible and nondeductible contributions both count against the same ceiling. Skipping the deduction does not let you contribute more.

Form 8606 and tracking your basis

Form 8606 is the most important piece of paper in this entire topic. It is a short form you attach to your tax return, and it does one crucial job. It records how much after-tax money you have put into your traditional IRAs. That running total is your basis.

Here is why it matters so much. Say you contribute 7,500 dollars of after-tax money this year and file Form 8606 to report it. Now your basis is 7,500 dollars. The IRS has an official record that you already paid tax on those dollars. Years later, when you take money out, that record ensures those specific dollars come back to you tax-free. Without the form, you have no proof, and the default assumption can be that the whole withdrawal is taxable.

You file a new Form 8606 for every year you make a nondeductible contribution, and the form carries your basis forward from year to year. Think of it as a logbook. Each entry adds to the running total, and that total is what protects you from double taxation down the road.

The single biggest favor you can do future-you is to file Form 8606 in every year you make a nondeductible contribution, and to keep copies. Basis you cannot prove is basis you may end up paying tax on twice.

If you have made nondeductible contributions in past years and never filed the form, do not panic. The IRS allows you to file Form 8606 for prior years to reconstruct your basis. It is more work than doing it on time, and it may require digging up old statements, but it can rescue basis you would otherwise lose. Publication 590-A and Publication 590-B on IRS.gov walk through the details.

How the growth gets taxed later

This is where a nondeductible IRA differs from a Roth, and the difference matters. Inside the account, everything grows tax-deferred. You do not pay tax on dividends, interest, or gains year to year. That part is a genuine benefit.

The catch shows up at withdrawal. Your after-tax basis, the money you already paid tax on, comes back out tax-free. But all the growth on top of that basis is taxed as ordinary income when you withdraw it. Not at the lower long-term capital gains rates you might get in a regular brokerage account. As ordinary income, at whatever your tax rate is in retirement.

Put that side by side with a Roth. In a Roth, both your contributions and all the growth can come out completely tax-free in retirement, once you meet the rules. So a nondeductible traditional IRA gives you tax-free return of your own basis but taxable growth, while a Roth gives you tax-free growth too. That gap is exactly why so many people who make nondeductible contributions want to move the money into a Roth as soon as they can. It also explains why leaving after-tax money sitting in a traditional IRA for decades is often not the goal.

The pro-rata rule and why it matters

Here is the rule that surprises the most people, so read this section slowly. When you take money out of a traditional IRA, or convert part of it to a Roth, you cannot choose to pull only your after-tax dollars. The IRS makes you treat every distribution as a proportional mix of your after-tax basis and your pretax money. That is the pro-rata rule.

And it gets stricter. For this calculation, the IRS lumps together every traditional IRA you own, plus any SEP IRA and SIMPLE IRA, and treats them as one big combined pool. It does not matter that the money sits in separate accounts at different firms. For pro-rata purposes, they are one account.

An example makes this concrete. Suppose you have an old rollover traditional IRA with 93,000 dollars of pretax money in it. This year you make a fresh 7,500 dollar nondeductible contribution into a different traditional IRA. Your combined IRA balance is now 100,500 dollars, and your after-tax basis is 7,500 dollars of that. Basis is about 7.46 percent of the total.

Now you try to convert 7,500 dollars to a Roth, hoping it is your tax-free basis. The pro-rata rule says otherwise. Only about 7.46 percent of that conversion, roughly 560 dollars, counts as tax-free return of basis. The other roughly 6,940 dollars is pretax money, and you owe ordinary income tax on it this year. You did not get to move your after-tax dollars cleanly. They stayed blended in.

This is the trap that ruins many do-it-yourself backdoor Roth attempts. People assume the new nondeductible contribution is the money that converts. Because of pro-rata, it almost never works that neatly when large pretax IRA balances already exist. The rule is the reason the backdoor Roth works best for people with little or no pretax IRA money to begin with.

The backdoor Roth, step by step

Now we can put the pieces together. The backdoor Roth is a two-step move that lets high earners get money into a Roth even though their income is above the Roth contribution limit. It relies on the fact that anyone can make a nondeductible contribution and, separately, anyone can convert traditional IRA money to a Roth regardless of income.

The clean version, for someone who has no pretax traditional IRA balances, looks like this. Step one, contribute after-tax money to a traditional IRA and file Form 8606 to record the basis. Step two, convert that money to a Roth IRA. Because the account holds only after-tax basis and little or no growth, the conversion triggers little or no tax. The money lands in the Roth, where it can grow tax-free from then on.

The reason this works cleanly only with no pretax IRA money goes right back to the pro-rata rule. If you have a big pretax IRA sitting around, the conversion drags a proportional share of that pretax money along with it, and you owe tax on that share. Some people solve this by first rolling their pretax IRA into a workplace 401k, if their plan allows it, because 401k money is not counted in the IRA pro-rata pool. That empties the IRA pool of pretax dollars and clears the way for a clean conversion. This is a well-known planning move, but it has real rules, so many people confirm the details with a tax professional before doing it.

One more note on timing. There is no required waiting period written into the law between the contribution and the conversion. Many people still let the transaction settle and keep clean records, because the paperwork matters more than the speed. The Form 8606 you file ties the whole thing together.

The most common mistakes

Two mistakes cause the vast majority of nondeductible IRA headaches, and both are avoidable once you know to watch for them.

Mistake one: forgetting Form 8606

This is the big one. You make a nondeductible contribution, you feel good about it, and you never file the form that records your basis. Years later, you or your tax preparer have no proof that part of the money was already taxed. The default treatment can make your withdrawals fully taxable, so you pay tax on the same dollars twice. File the form every single year you make a nondeductible contribution, and keep copies with your permanent tax records. It is a small task that protects real money.

Mistake two: the pro-rata trap with existing pretax money

The second mistake is attempting a backdoor Roth while a large pretax IRA balance is sitting in the background. People expect their fresh after-tax contribution to convert tax-free, then get a surprise tax bill because the pro-rata rule blended in the pretax dollars. Before you attempt a backdoor Roth, take stock of every traditional, SEP, and SIMPLE IRA you own. If there is meaningful pretax money in any of them, understand that the conversion will be partly taxable, or look into whether rolling that pretax money into a 401k first makes sense for you.

A few smaller pitfalls

Beyond the big two, watch for these. Contributing more than the annual limit across all your IRAs creates an excess contribution that carries its own penalty until you fix it. Contributing without enough earned income to support it is not allowed. And assuming the phaseout figures you used three years ago still apply this year can lead to a wrong deduction. The numbers move, so check the current year.

Is a nondeductible IRA right for you?

A nondeductible IRA earns its keep in a few clear situations. If you are a high earner blocked from deducting a traditional contribution and blocked from a Roth, it may be your on-ramp to a backdoor Roth. If you simply want more tax-deferred growth after maxing out other accounts, it can serve that purpose too, as long as you accept that the growth will be taxed as ordinary income later.

For many savers, though, the after-tax money does not stay in the traditional IRA for long. It gets converted to a Roth, where growth is tax-free. That is often the whole point. The traditional IRA is just the doorway, and the nondeductible contribution is the key that fits the lock.

Whatever path you take, the two habits that keep you out of trouble are the same. File Form 8606 every year you make a nondeductible contribution, and understand the pro-rata rule before you convert anything. Get those two right and the rest is straightforward. This is education rather than personal advice, so for a plan tailored to your own numbers, a tax professional can be well worth the fee, especially the first time you run a backdoor Roth.