A backdoor Roth IRA allows high earners to make a nondeductible traditional IRA contribution and then convert it to a Roth IRA. However, existing pretax IRA balances can make part of that conversion taxable under the pro-rata rule. This guide explains which balances count, why year-end values matter, and what to check before converting.
Key Takeaways
- A backdoor Roth IRA generally combines a nondeductible traditional IRA contribution with a Roth conversion.
- The pro-rata rule considers your combined traditional IRA balances, including traditional SEP and SIMPLE IRAs.
- Opening a separate IRA does not isolate your after-tax contribution from existing pretax money.
- December 31 balances in the conversion year affect the calculation, even when you convert earlier.
- Form 8606 tracks nondeductible contributions and helps determine the taxable portion of a conversion.
You contribute after-tax money to a traditional IRA, convert it to Roth, and expect little or no additional tax.
Then an old rollover IRA changes the calculation.
For high earners, the mechanics of a backdoor Roth IRA can look straightforward. The tax treatment depends on retirement accounts beyond the one used for the transaction.
Before converting, review your existing IRA balances, contribution history, and any rollovers planned for later in the year. This checklist explains what to check and why it matters.
What Is a Backdoor Roth IRA?
A backdoor Roth IRA is a strategy that generally involves making a nondeductible contribution to a traditional IRA and then converting money from that IRA to a Roth IRA.
“Backdoor Roth” is an informal name for the process, not a separate account type.
High earners may consider it when their income limits or prevents a direct Roth IRA contribution. Income restrictions on direct Roth contributions do not apply in the same way to Roth conversions.
However, the initial contribution still requires eligible compensation and available IRA contribution room. For 2026, the combined traditional and Roth IRA contribution limit is $7,500, or $8,600 for eligible individuals age 50 or older. Your compensation can impose a lower limit.
A conversion does not create a second annual contribution allowance. It changes the tax status of money already held in an eligible retirement account.
How Does the Pro-Rata Rule Work?
The pro-rata rule determines how much of an IRA distribution or conversion represents after-tax basis and how much represents taxable money.
Basis generally includes nondeductible IRA contributions that have not already been recovered tax-free. Keep records of that basis so it is not taxed again.
When your IRAs contain both basis and pretax money, you generally cannot choose to convert only the after-tax dollars. The calculation looks across your own traditional IRAs, including traditional SEP and SIMPLE IRAs. Separate account numbers or custodians do not avoid aggregation.
For a straightforward case, the approximate calculation is:
Nontaxable percentage = Available IRA basis ÷ Combined year-end IRA value plus relevant distributions and conversions during the year.
Form 8606 applies the detailed calculation, including adjustments for contribution timing and certain other transactions. The formula above is a planning illustration, not a substitute for completing the form.
A Hypothetical Pro-Rata Example
Assume you are under age 50 and:
- Have $92,500 in an existing pretax rollover IRA
- Make a $7,500 nondeductible IRA contribution for 2026
- Convert $7,500 during 2026
- Have no investment changes, other distributions, or additional contributions
- Finish December 31 with $92,500 in your traditional IRAs
| Calculation | Amount |
| Available after-tax basis | $7,500 |
| Year-end IRA balance plus conversion | $100,000 |
| Nontaxable percentage | 7.5% |
| Nontaxable portion of the $7,500 conversion | $562.50 |
| Taxable portion of the conversion | $6,937.50 |
Although the new contribution used after-tax money, most of the conversion is taxable under these assumptions.
The unused $6,937.50 of basis remains available for future calculations. It does not disappear.
Your Backdoor Roth IRA Pro-Rata Checklist
Complete these checks before requesting a conversion.
1. Confirm Whether You Need the Backdoor Approach
Check your eligibility for a direct Roth IRA contribution first.
For 2026, direct Roth IRA contributions phase out at modified adjusted gross income of:
- $153,000–$168,000 for single filers and heads of household
- $242,000–$252,000 for married couples filing jointly
Different rules apply to married filing separately, including a $0–$10,000 range for those who lived with their spouse during the year.
If you qualify for a full direct contribution, the backdoor process may add unnecessary steps.
2. Inventory Your IRA Accounts
Review accounts across every custodian, including old accounts you no longer actively manage.
| Account | Generally Included in Your IRA Pro-Rata Calculation? |
| Traditional IRA | Yes |
| Traditional rollover IRA | Yes |
| Traditional SEP IRA | Yes |
| Traditional SIMPLE IRA | Yes |
| Roth IRA | No |
| Money remaining in a 401(k) or 403(b) | No |
| Your spouse’s separately owned IRAs | No |
Inherited IRAs can require separate treatment. Ask your tax professional to review them rather than automatically combining them with your own accounts.
Each spouse calculates their own IRA basis and distributions, even when filing a joint return.
3. Locate Your Prior Form 8606 Records
Find previous Forms 8606 and supporting contribution records.
An IRA’s market value does not tell you how much after-tax basis it contains. Old nondeductible contributions may still affect the current calculation.
If records are incomplete, reconcile them before assuming the entire balance is pretax or after-tax.
4. Project Your December 31 Balance
Review the year-end balance for the calendar year in which the conversion occurs.
A conversion early in the year does not lock in the tax result. A later rollover from a former employer’s 401(k) into a traditional IRA can introduce pretax money into the year-end calculation.
Likewise, having a zero balance on conversion day does not establish a zero balance for December 31. Outstanding rollovers can require additional adjustments.
5. Account for Earnings Before Conversion
Even with no other pretax IRA balances, investment earnings can create a taxable amount.
Suppose a $7,500 nondeductible contribution grows to $7,550 before you convert the entire account. With no other relevant IRA balances or transactions, the $50 of growth would generally be taxable.
Converting promptly can limit intervening earnings. It does not eliminate the effect of pretax money elsewhere.
6. Separate the Contribution Year From the Conversion Year
A contribution and conversion can belong to different tax years.
For example, an eligible contribution made in early 2027 may be designated for 2026 if completed by the applicable contribution deadline. A conversion completed in 2027 belongs to 2027.
That can mean reporting the nondeductible contribution on a 2026 Form 8606 and the conversion on a 2027 Form 8606. Use the forms and instructions applicable to each year.
7. Review the Expected Tax Before Authorizing the Conversion
Estimate the taxable amount alongside your other income.
A conversion can affect income-based tax calculations beyond its immediate federal tax cost. State treatment may also matter.
Confirm how any tax will be paid. Withholding from retirement funds reduces the amount reaching Roth and may create additional consequences.
What If You Already Have Pretax IRA Money?
An existing pretax balance does not prohibit a backdoor Roth IRA. It changes the planning.
Evaluate a Rollover Into an Employer Plan
Some employer plans accept eligible pretax IRA money.
If your plan permits it, moving eligible pretax amounts into the plan may reduce the traditional IRA balance used in the pro-rata calculation. After-tax IRA basis cannot simply be rolled into a qualified plan with those pretax dollars.
Confirm eligibility, plan acceptance, and completion timing. SIMPLE IRA rollover restrictions, including the initial two-year period, need separate attention.
Also compare plan fees, investment choices, and withdrawal provisions before moving assets.
Consider a Taxable Conversion Deliberately
You may decide to convert pretax money and pay the associated tax.
That is a broader Roth conversion decision. Model the amount against your current tax situation and expected future needs before proceeding.
Postpone the Transaction
If the tax cost or administrative work does not fit your circumstances, postponing can be reasonable.
Your available savings should support your overall plan, including liquidity needs and other retirement options.
Reporting Mistakes to Avoid
The IRS Form 8606 overview identifies nondeductible contributions and Roth conversions among the transactions the form reports.
Common mistakes include:
- Treating a nondeductible contribution as an income tax deduction
- Reporting the entire conversion as tax-free without checking other IRA balances
- Omitting previously accumulated basis
- Reporting a conversion in the contribution year instead of the actual conversion year
- Ignoring a rollover completed later in the year
Keep Forms 1099-R and 5498, conversion confirmations, and year-end statements with your tax records.
Roth conversions made after 2017 cannot be reversed through recharacterization. Review the transaction before authorizing it.
Frequently Asked Questions
Can I Avoid the Pro-Rata Rule by Opening a New IRA?
No. Your relevant IRA accounts are generally aggregated for the calculation. A separate account does not isolate newly contributed after-tax dollars.
Does My Spouse’s IRA Affect My Conversion?
Generally, no. Each spouse’s IRA calculation is separate, including on a joint return.
Does a 401(k) Balance Count?
Money remaining in a 401(k) does not enter the IRA pro-rata calculation. Rolling it into a traditional IRA can change that result.
Is a Backdoor Roth the Same as a Mega Backdoor Roth?
No. A backdoor Roth generally starts with a nondeductible traditional IRA contribution. A mega backdoor Roth uses eligible non-Roth after-tax workplace plan contributions and requires specific plan features.
Can High Earners Make Nondeductible Traditional IRA Contributions?
Generally, yes, if they meet compensation and contribution requirements. High income can restrict deductibility without prohibiting the contribution itself.
Check the Full IRA Picture Before Converting
A backdoor Roth IRA can provide a route to Roth savings when direct contributions are limited. The tax result depends on your combined IRA position and the transactions completed throughout the year.
Before converting, assemble your account statements and prior Forms 8606. Have your tax professional review the expected December 31 balances and calculate the taxable amount.
Explore Clair360 to learn how ClairFi supports coordinated tax and wealth planning, or connect with the ClairFi team.
This article provides general education using 2026 contribution limits. Review your circumstances with a qualified tax professional before implementing a conversion.
