Form 8606 Nondeductible IRA Calculator 2026 β Pro-Rata Rule & Basis Tracker
Calculate the taxable portion of your IRA distribution or Roth conversion using the pro-rata rule. Track nondeductible IRA basis across multiple years.
$
Line 14 from last year's Form 8606 (0 if first year) $
2026 limit: $7,000 ($8,000 if age 50+) $
All traditional/SEP/SIMPLE IRAs combined at year-end $
Amount withdrawn or converted to Roth this year $0
Taxable Portion of Distribution
$0
Non-Taxable (Return of Basis)
$0
Remaining Basis (New Line 14)
$0
Estimated Tax on Distribution
Form 8606 Calculation (Pro-Rata Rule)
How the Pro-Rata Rule Works
The IRS treats all your traditional IRA money as one pool. When you take a distribution, you cannot choose to withdraw only after-tax dollars first. Instead, the taxable percentage equals the ratio of pre-tax money to total IRA balance.
The Formula
Total basis = prior year basis + current year nondeductible contribution
Non-taxable ratio = total basis / (total IRA balance + distribution)
Non-taxable amount = distribution Γ non-taxable ratio
Taxable amount = distribution β non-taxable amount
New basis (Line 14) = total basis β non-taxable amount
Non-taxable ratio = total basis / (total IRA balance + distribution)
Non-taxable amount = distribution Γ non-taxable ratio
Taxable amount = distribution β non-taxable amount
New basis (Line 14) = total basis β non-taxable amount
Example
Prior basis $7,000, new contribution $7,000, total IRA balance $80,000, distribution $10,000:
Total basis = $7,000 + $7,000 = $14,000
Denominator = $80,000 + $10,000 = $90,000
Non-taxable ratio = $14,000 / $90,000 = 15.56%
Non-taxable amount = $10,000 Γ 15.56% = $1,556
Taxable amount = $10,000 β $1,556 = $8,444
New basis = $14,000 β $1,556 = $12,444
Total basis = $7,000 + $7,000 = $14,000
Denominator = $80,000 + $10,000 = $90,000
Non-taxable ratio = $14,000 / $90,000 = 15.56%
Non-taxable amount = $10,000 Γ 15.56% = $1,556
Taxable amount = $10,000 β $1,556 = $8,444
New basis = $14,000 β $1,556 = $12,444
Extended
Multi-Year Basis Tracker
Enter up to 5 years of contributions and distributions to see how your IRA basis evolves over time
Enter up to 5 years of contributions and distributions to track how your IRA basis changes over time.
$
$
$
$
$
$
$
$
$
$
$
$
$
$
$
Multi-Year Basis Evolution
| Year | Contribution | Total Basis | Distribution | Non-Taxable | Taxable | Remaining Basis |
|---|
Frequently Asked Questions
What is Form 8606 and when do I need it?
Form 8606 is filed with your tax return whenever you make a nondeductible contribution to a traditional IRA, convert a traditional IRA to a Roth IRA, or take distributions from a traditional IRA that contains after-tax (nondeductible) contributions. It tracks your "basis" β the after-tax money in your IRA β so you are not taxed twice on those dollars when you withdraw them.
What is the pro-rata rule for IRA distributions?
The pro-rata rule treats all your traditional IRA money as a single pool. When you take a distribution or do a Roth conversion, the taxable portion is calculated as: (total IRA balance β total basis) / total IRA balance Γ distribution amount. You cannot cherry-pick which dollars you withdraw first β the IRS requires you to average your basis across all traditional IRAs.
How do I find my prior basis from Form 8606?
Your prior IRA basis is on line 14 of the most recent Form 8606 you filed. If you have never made nondeductible contributions or conversions before, your basis is $0. Keep all your old Form 8606s permanently β they are your legal record of after-tax contributions and must be carried forward every year until your basis reaches zero.
Can I avoid the pro-rata rule with a backdoor Roth IRA?
The pro-rata rule affects the backdoor Roth IRA strategy. If you have other pre-tax traditional IRA money, your nondeductible contribution gets mixed in and most of your conversion becomes taxable. One common workaround is to roll your pre-tax IRA money into a 401(k) before year-end, leaving only the nondeductible amount in the IRA for a clean conversion.
What is the nondeductible IRA contribution limit for 2026?
The IRA contribution limit for 2026 is $7,000 ($8,000 if age 50 or older). If your income is too high to deduct a traditional IRA contribution, or you are covered by a workplace plan above the deductibility thresholds, you can still make a nondeductible contribution up to these limits and track your basis on Form 8606.