Quick Answer
The pro-rata rule requires all traditional IRA conversions to be treated as a proportional mix of pre-tax and after-tax dollars. If you have $90,000 in deductible IRA contributions and $10,000 in non-deductible contributions, any conversion is 90% taxable regardless of which dollars you intend to convert.
Best Answer
Robert Kim, CPA
Best for investors who have both deductible and non-deductible traditional IRA contributions
How the pro-rata rule works
The pro-rata rule, codified in IRC Section 408A(d)(4), treats all of your traditional IRAs as one big account when calculating the tax consequences of a Roth conversion. You cannot cherry-pick which dollars to convert — the IRS requires a proportional calculation based on your total IRA balance.
The formula is straightforward: (Total after-tax contributions ÷ Total IRA balance) × Conversion amount = Non-taxable portion
Example: $100,000 conversion with mixed contributions
Let's say you have:
You want to convert $100,000 to a Roth IRA. Here's how the pro-rata rule applies:
1. After-tax percentage: $18,000 ÷ $220,000 = 8.18%
2. Non-taxable portion of conversion: $100,000 × 8.18% = $8,180
3. Taxable portion: $100,000 - $8,180 = $91,820
Even if you specifically intended to convert your $18,000 in non-deductible contributions first, you'd still owe taxes on $91,820 of the conversion.
The aggregation rule makes it worse
According to IRS Publication 590-A, the pro-rata rule applies to ALL your traditional IRAs combined — including SEP-IRAs and SIMPLE IRAs (after the 2-year waiting period). You cannot maintain separate "buckets" to avoid this calculation.
Non-taxable percentage: $20,000 ÷ $220,000 = 9.09%
Key factors that affect the pro-rata calculation
What you should do
Before any Roth conversion, calculate your exact pro-rata percentage using Form 8606 from your most recent tax return. If you have substantial pre-tax IRA balances, consider the backdoor Roth strategy limitations or explore other tax-advantaged accounts first.
Use our return scanner to identify all your IRA contributions and balances from previous years to ensure accurate pro-rata calculations.
Key takeaway: The pro-rata rule makes selective Roth conversions impossible — every conversion includes a proportional mix of taxable and non-taxable dollars based on your total traditional IRA balance.
*Sources: IRC Section 408A(d)(4), IRS Publication 590-A*
Key Takeaway: The pro-rata rule requires all Roth conversions to include a proportional mix of pre-tax and after-tax dollars based on your total traditional IRA balance — you cannot selectively convert only non-deductible contributions.
Pro-rata rule impact on different IRA balance scenarios
| Total IRA Balance | Non-deductible Basis | Non-taxable % | $50K Conversion Taxable Amount |
|---|---|---|---|
| $100,000 | $10,000 | 10% | $45,000 |
| $200,000 | $20,000 | 10% | $45,000 |
| $500,000 | $25,000 | 5% | $47,500 |
| $1,000,000 | $50,000 | 5% | $47,500 |
More Perspectives
Michelle Woodard, JD
Best for high-income earners who cannot contribute directly to Roth IRAs
The backdoor Roth killer
For high earners above the Roth IRA contribution limits ($153,000 single/$228,000 MFJ in 2026), the backdoor Roth strategy becomes problematic when you have existing traditional IRA balances.
The backdoor Roth process:
1. Make non-deductible traditional IRA contribution ($7,000 in 2026)
2. Immediately convert to Roth IRA
3. Pay taxes only on growth (minimal if done quickly)
But the pro-rata rule ruins this strategy. If you have $350,000 in rollover IRAs from old 401(k)s and make a $7,000 backdoor Roth conversion:
You'd owe taxes on 98% of your "backdoor" conversion, defeating the entire purpose.
Solutions for high earners
1. Roll traditional IRAs into current 401(k): Many employer plans accept rollover contributions, clearing your IRA balances
2. Use mega backdoor Roth instead: After-tax 401(k) contributions converted to Roth avoid IRA pro-rata rules
3. Consider timing: Make the traditional IRA contribution and conversion in a year when you have minimal IRA balances
The pro-rata rule has killed many high-earner tax strategies, making employer plan optimization crucial for Roth conversion planning.
Key Takeaway: High earners with existing traditional IRA balances cannot effectively use the backdoor Roth strategy due to pro-rata taxation — consider rolling IRAs into employer plans first.
Robert Kim, CPA
Best for retirees doing multi-year Roth conversion strategies
Multi-year conversion planning
Retirees often have the lowest tax rates of their lives between retirement and age 73 (when RMDs begin), making this the optimal window for Roth conversions. However, the pro-rata rule affects every year of a multi-year strategy.
Example: 5-year conversion plan
Starting balances:
Planning to convert $150,000 annually for 6 years:
The percentage stays relatively stable across years because both taxable and non-taxable portions grow proportionally, but market performance and RMD requirements can shift the calculation.
Coordination with Social Security and Medicare
The taxable portion of Roth conversions counts as income for:
Retirees must factor the pro-rata rule into broader tax planning to avoid pushing themselves into higher brackets or triggering additional Medicare costs.
Key Takeaway: Retirees doing systematic Roth conversions must account for pro-rata taxation in multi-year planning, especially when coordinating with Social Security and Medicare income thresholds.
Sources
- IRS Publication 590-A — Contributions to Individual Retirement Arrangements (IRAs)
- IRC Section 408A(d)(4) — Roth IRA distribution and conversion rules
Related Questions
Reviewed by Michelle Woodard, JD on February 28, 2026
This content is for educational purposes only and is not a substitute for professional tax advice. Consult a qualified tax professional for advice specific to your situation.