Nondeductible IRA Contributions: Rules, Tracking, and the Backdoor Roth Connection

If you earn too much to deduct a traditional IRA contribution but still want to use an IRA, you can make a nondeductible contribution. You will not get an upfront tax break, but the money still grows tax-deferred — and nondeductible contributions are the foundation of the popular backdoor Roth IRA strategy. The catch: you need to track your after-tax basis carefully using Form 8606 to avoid double taxation.

Key Takeaways

• Anyone with earned income can make a traditional IRA contribution -- but it may not be deductible.
• Nondeductible contributions create 'basis' in your IRA that is not taxed again on withdrawal.
• Form 8606 is required to track your basis and must be filed every year you contribute after-tax dollars.
• Nondeductible contributions are the first step in the backdoor Roth IRA strategy.

When Are IRA Contributions Nondeductible?

You can always contribute to a traditional IRA if you have earned income and are under the contribution limit. But the deductibility of that contribution depends on two factors: whether you (or your spouse) have access to a workplace retirement plan, and your income level.

Deduction Phase-Out Ranges (2025 / 2026)

If your MAGI is above the upper limit of the phase-out range and you are covered by a workplace plan, your traditional IRA contribution is fully nondeductible. If you fall within the range, it is partially deductible.

IRA Contribution Limits

Regardless of deductibility, the contribution limits are the same:

These limits apply to your total traditional and Roth IRA contributions combined. You cannot contribute $7,000 to a traditional IRA and another $7,000 to a Roth IRA in the same year.

Form 8606: Tracking Your Basis

Form 8606 (Nondeductible IRAs) is the critical document that establishes and tracks your basis — the amount of after-tax money in your traditional IRA.

When to File Form 8606

You must file Form 8606 when you:

1. Make nondeductible contributions to a traditional IRA
2. Convert from a traditional IRA to a Roth IRA
3. Take distributions from a traditional IRA that contains after-tax money
4. Take distributions from a Roth IRA before meeting the 5-year/age-59.5 requirements

How Basis Tracking Works

Example: Over three years, you contribute $7,000 per year to a nondeductible traditional IRA, for a total basis of $21,000. The account grows to $25,000.

• Basis (after-tax money): $21,000
• Earnings (pre-tax money): $4,000
• Total IRA value: $25,000

When you withdraw, each distribution is a proportional mix of basis and earnings. You cannot withdraw only the basis first — this is the pro-rata rule.

Filing Form 8606

Form 8606 goes with your Form 1040. The key sections:

• Part I: Nondeductible contributions made for the year and cumulative basis
• Part II: Conversions from traditional to Roth IRA (pro-rata calculation)
• Part III: Distributions from Roth IRAs

Keep copies of every Form 8606 you file. The IRS tracks cumulative basis from year to year, but having your own records prevents problems.

The Pro-Rata Rule

The pro-rata rule is the most common source of confusion with nondeductible IRA contributions. It applies when you convert or withdraw from a traditional IRA that contains both pre-tax and after-tax money.

How It Works

The IRS treats all of your traditional IRAs as one pool when calculating the taxable portion of any conversion or distribution. This includes:

• Traditional IRAs
• SEP IRAs
• SIMPLE IRAs (after the 2-year holding period)

Example: You have:

• $7,000 nondeductible traditional IRA (basis = $7,000)
• $63,000 in a rollover IRA from a prior 401(k) (basis = $0)
• Total IRA balance: $70,000
• Total basis: $7,000

If you convert $7,000 to a Roth IRA, the taxable portion is:

Taxable % = 1 - ($7,000 basis / $70,000 total) = 90%

So $6,300 of your $7,000 conversion is taxable, and only $700 is tax-free.

How to Avoid the Pro-Rata Rule

• Roll pre-tax IRA money into your 401(k): If your employer plan accepts incoming rollovers, move your pre-tax IRA balances into the 401(k) (see our 401(k) to IRA rollover guide for how reverse rollovers work). This leaves only the nondeductible basis in the IRA, making a Roth conversion nearly tax-free.
• Convert everything: If the total tax bill is manageable, convert the entire IRA balance to Roth. All basis is used up, and you start fresh. For large balances, a Roth conversion ladder can spread the tax hit across multiple years.
• Do not make nondeductible contributions if you have large pre-tax IRA balances and cannot roll them into a workplace plan.

The Backdoor Roth IRA Strategy

The backdoor Roth IRA is the primary reason people make nondeductible IRA contributions. Here is the strategy in brief:

1. Contribute to a traditional IRA (nondeductible, since your income is too high for a deduction or direct Roth contribution)
2. Convert the traditional IRA to a Roth IRA (shortly after contributing)
3. Pay little or no tax on the conversion (because the contribution was already after-tax)

This works cleanly when you have no other pre-tax IRA balances (avoiding the pro-rata rule).

For a complete walkthrough, see our backdoor Roth IRA strategy guide.

Roth IRA Income Limits (for Reference)

These are the limits that make direct Roth contributions unavailable and push higher earners toward the backdoor strategy:

Common Mistakes to Avoid

1. Not Filing Form 8606

Without Form 8606, the IRS has no record of your basis. You will be taxed again on money you already paid tax on. File retroactively if you missed it (the penalty is only $50).

2. Ignoring the Pro-Rata Rule

Many people assume they can convert just their nondeductible contribution tax-free while keeping pre-tax IRA money untouched. The IRS does not allow this — all IRA balances are aggregated.

3. Contributing to a Nondeductible IRA Without a Conversion Plan

If you are not planning to convert to Roth, a nondeductible traditional IRA is generally a poor choice. Understanding the Roth vs. traditional tax tradeoffs is key here: the earnings grow tax-deferred but are taxed as ordinary income on withdrawal — worse than holding investments in a taxable account where you would get capital gains rates.

4. Forgetting Spousal IRA Rules

A non-working spouse can make IRA contributions based on the working spouse’s income. The deductibility rules differ when the non-working spouse is not covered by a workplace plan — the phase-out range is much higher ($236,000-$246,000 MFJ in 2025).

Nondeductible IRA vs. Other Options

Learn more about each option: HSA triple tax advantage, mega backdoor Roth, and 529 plans tax benefits.

DIY Checklist: Nondeductible IRA Contributions

• Confirm you have earned income equal to or exceeding your contribution amount
• Check the deduction phase-out table to confirm your contribution is nondeductible
• Make the contribution to your traditional IRA (by April 15 of the following year)
• File Form 8606, Part I with your tax return
• If doing a backdoor Roth: convert to Roth IRA (check pro-rata rule first)
• File Form 8606, Part II for the conversion year
• Keep copies of all Form 8606 filings for your records
• Confirm your total traditional + Roth IRA contributions do not exceed the annual limit

How sharper.tax Helps

When you upload your tax return to sharper.tax, our analysis identifies whether you are eligible for direct Roth contributions, whether the backdoor Roth strategy is viable given your existing IRA balances, and how much you could save through Roth conversion strategies. We model the pro-rata impact using your actual account balances so you can make an informed decision rather than relying on generic advice.

Related Guides

• Traditional IRA Guide — deduction rules, contribution limits, and withdrawal strategies
• IRA to Roth Conversion Guide — step-by-step process for converting pre-tax IRA money to Roth
• Roth Conversion Ladder — spreading conversions across multiple years to manage the tax hit
• Roth vs. Traditional Tax Tradeoffs — how to decide which account type works best for your situation
• Inherited IRA Rules — distribution requirements for IRAs you inherit from someone else
• Backdoor Roth IRA Strategy — the complete walkthrough for converting nondeductible contributions to Roth

Sources

• IRS Form 8606 Instructions
• IRS Publication 590-A: Contributions to IRAs
• IRS Publication 590-B: Distributions from IRAs
• IRS: 2025 IRA Contribution and Deduction Limits

The information above is educational and not tax advice.