401k vs Roth IRA
Independent Retirement Guide
Per 26 U.S.C. § 408A(d)(3)

Backdoor Roth IRA in 2026

If your modified AGI exceeds the IRS Notice 2025-67 Roth IRA phase-out (26 U.S.C. § 408A(c)(3)), the backdoor Roth mechanism under § 408A(d)(3) gives you Roth tax treatment on $7,500 of contributions per year. Here is the statutory mechanism, the § 408(d)(2) pro-rata trap, IRS Form 8606 reporting, and the mega backdoor under IRS Notice 2014-54 for plans that allow it.

Authority feed: Figures sourced from IRS Publication 575, IRS Publication 590-A, and IRS Notice 2025-67. Last verified 2026-05-27; next IRS COLA notice expected 2026-11-11. Full methodology and source ledger.
Who needs the backdoor (per IRS Notice 2025-67)

You earn above the 2026 § 408A(c)(3) phase-out

  • Single filer with modified AGI above $168,000
  • Married filing jointly with modified AGI above $252,000
  • Married filing separately with modified AGI above $10,000

At those incomes you cannot contribute directly to a Roth IRA per 26 U.S.C. § 408A(c)(3). The backdoor route uses a non-deductible Traditional IRA contribution under § 408(o) followed by a conversion under § 408A(d)(3). Both are tracked on IRS Form 8606.

What you gain

$7,500 of Roth IRA space per year

At a 7 percent return for 25 years, $7,500 per year compounds to roughly $475,000. That balance grows tax free and is never subject to RMDs in your lifetime. Couples both contribute, doubling the figure.

The mechanism

The two step process, in order

Both steps happen at the same custodian. Most major brokerages have a backdoor Roth workflow built in.

  1. 1

    Contribute non-deductible to a Traditional IRA under § 408(o)

    Contribute up to $7,500 (or $8,600 at 50+ per 26 U.S.C. § 219(b)(5)(B)) to a Traditional IRA. Do not take the deduction. File IRS Form 8606 to track non-deductible basis as required by 26 U.S.C. § 408(o)(4).

  2. 2

    Convert the Traditional IRA to a Roth IRA under § 408A(d)(3)

    Initiate a Roth conversion at your custodian per 26 U.S.C. § 408A(d)(3) and IRS Publication 590-A 'Converting'. If you contributed $7,500 and convert $7,500 the same week, the taxable portion is roughly zero (any growth between contribution and conversion is ordinary income).

  3. 3

    Confirm § 408(d)(2) pro-rata is clean

    The pro-rata rule in 26 U.S.C. § 408(d)(2) treats all your IRAs as one pool. If you have any pre-tax IRA balance (Traditional, SEP, SIMPLE), the conversion will be partially taxable. Roll those balances into a 401(k) first; 401(k) plans are excluded from the IRA pro-rata pool per IRS Publication 590-A 'Are Distributions Taxable?'

  4. 4

    Report on IRS Form 8606 and repeat next January

    Form 8606 Part I tracks the non-deductible contribution; Part II tracks the conversion. Most people repeat the process every January 1 to maximise tax-free growth duration.

26 U.S.C. § 408(d)(2)

The pro-rata rule, with numbers

The pro-rata rule looks at all your Traditional, SEP, and SIMPLE IRA balances together when calculating tax on a conversion. Per IRS Publication 590-A 'Are Distributions Taxable?', 401(k) and 403(b) balances are NOT included in the IRA pool.

Example
You have $90,000 of pre tax IRA assets and contribute $7,500 non deductible
  • Total IRA basis: $97,500 ($90,000 pre tax plus $7,500 after tax)
  • Pre tax fraction: 90,000 divided by 97,500 = 92.3 percent
  • If you convert $7,500: 92.3 percent ($6,923) is taxable as ordinary income
  • Only 7.7 percent ($577) of the conversion is tax free

The fix: roll the $90,000 of pre tax IRA balances into a 401k or solo 401k before converting. Once the IRA pool is empty of pre tax dollars, the pro rata fraction is zero and the conversion is fully tax free.

If your plan allows

Mega backdoor Roth via 401k after-tax contributions

Some 401(k) plans permit voluntary after-tax contributions on top of the § 402(g) employee deferral, against the § 415(c) annual additions cap. Combined with in-plan Roth conversions (SECURE 2.0 § 604 / 26 U.S.C. § 402A(g)) or in-service distributions per IRS Notice 2014-54, this opens up tens of thousands of additional Roth space per year. See /mega-backdoor-roth for the deep dive.

2026 mega backdoor headroom (per IRS Notice 2025-67)
§ 415(c) combined annual additions cap: $72,000
Less § 402(g) employee deferral: $24,500
Less employer match (example 4% of $200k): $8,000
Available voluntary after-tax contribution: $39,500
Plan requirements (verify in SPD per ERISA § 102)
  • Plan permits voluntary after-tax contributions (allocated against § 415(c))
  • Plan offers in-plan Roth conversions under 26 U.S.C. § 402A(g) (SECURE 2.0 § 604) OR in-service distributions of after-tax balance per IRS Notice 2014-54
  • Custodian processes the after-tax-to-Roth sweep promptly to limit taxable earnings
  • Confirm against your Summary Plan Description (ERISA § 102; 29 U.S.C. § 1022) before relying on it
Revised priority for high earners

Contribution order with backdoor mechanics

  1. 1. 401k up to the full employer match (ERISA § 203 vesting clock)
  2. 2. Backdoor Roth IRA, $7,500 (or $8,600 at 50+ per 26 U.S.C. § 219(b)(5)(B))
  3. 3. Max 401k toward the $24,500 § 402(g) employee cap
  4. 4. Mega backdoor Roth against § 415(c) $72,000 headroom if the plan permits after-tax and conversion
  5. 5. HSA if eligible: $4,300 individual or $8,550 family per IRS Pub 969
  6. 6. Taxable brokerage with tax-efficient funds (long-term capital gains under 26 U.S.C. § 1(h))
Frequently asked

Backdoor Roth questions

Is the backdoor Roth IRA still legal in 2026?+

Yes. The conversion mechanism under 26 U.S.C. § 408A(d)(3) remains legal in 2026. Build Back Better Act provisions to eliminate it did not pass into law, and no current 2026 legislation changes that. The strategy depends on the statutory ability to make a non-deductible Traditional IRA contribution (26 U.S.C. § 408(o)) and then convert to a Roth (26 U.S.C. § 408A(d)(3)). Report the non-deductible basis on IRS Form 8606. Confirm with current IRS guidance and a tax professional before relying on the strategy.

What is the pro rata rule?+

The pro-rata rule in 26 U.S.C. § 408(d)(2) treats all your Traditional, SEP, and SIMPLE IRA balances as a single pool when determining how much of a conversion is taxable. If 90 percent of your IRA balance is pre-tax, then 90 percent of any conversion is taxable, even if the converted dollars came from a non-deductible contribution. Per IRS Publication 590-A 'Are Distributions Taxable?' you roll pre-tax IRA balances into a 401(k) (the 401(k) is excluded from the pro-rata calculation) before converting to neutralise this.

How much can I put through the mega backdoor Roth in 2026?+

The mega backdoor Roth uses after-tax contributions inside a 401(k). The combined annual additions cap under 26 U.S.C. § 415(c) is $72,000 in 2026 per IRS Notice 2025-67 § III.A. Subtract your employee deferral ($24,500 under § 402(g)) and employer match to get the headroom for after-tax contributions. Typical headroom is $20,000 to $40,000 depending on the match. The conversion mechanism is either in-plan Roth conversion under SECURE 2.0 § 604 / 26 U.S.C. § 402A(g) or in-service distribution + rollover per IRS Notice 2014-54. See /mega-backdoor-roth.

Should I do a backdoor Roth before or after maxing my 401k?+

After capturing the employer match and before fully maxing the 401k. Order: 1) 401k to match, 2) backdoor Roth IRA $7,500 per IRS Notice 2025-67, 3) max 401k toward $24,500 § 402(g) cap, 4) mega backdoor Roth against § 415(c) headroom if the plan allows, 5) HSA per IRS Pub 969, 6) taxable brokerage. The Roth IRA bucket is more flexible (Pub 590-B ordering rules: contributions accessible any time), so it is worth filling early.

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