Backdoor Roth IRA

Why the Backdoor exists

Congress set Roth IRA income limits to keep the benefit aimed at middle-income workers. In 2026, direct Roth contributions phase out between $150,000–$165,000 single and $236,000–$246,000 married filing jointly. Above those thresholds, you cannot contribute directly to a Roth.

But Roth conversions, moving money from a Traditional IRA to a Roth IRA, have had no income limit since 2010. The Backdoor Roth exploits that gap: contribute to a Traditional IRA with no deduction, then convert to Roth immediately. The IRS has formally acknowledged the technique multiple times; it is not a tax-shelter grey area.

The four-step mechanics

1. Open a Traditional IRA and a Roth IRA at the same brokerage (Fidelity, Schwab and Vanguard all support this in a few clicks).
2. Contribute up to $7,000 ($8,000 if 50+) to the Traditional IRA. Do not take the deduction on your tax return, it's a non-deductible contribution.
3. Wait until the cash settles (1–3 business days), then initiate a conversion from the Traditional IRA to the Roth IRA. Convert the full balance.
4. When you file taxes, complete IRS Form 8606 to report the non-deductible contribution and the conversion. This is the critical paperwork step.

The pro-rata rule, simply

The single landmine is the pro-rata rule. The IRS treats all of your Traditional, SEP and SIMPLE IRA balances as one combined pool for conversion-tax purposes. If you have any pre-tax dollars in any IRA, your conversion will be partially taxable in proportion to the pre-tax share of the total pool.

Example: $7,000 non-deductible contribution + $63,000 pre-tax balance in a rollover IRA = a $70,000 pool that's 90% pre-tax. Converting $7,000 = $6,300 taxable conversion + only $700 tax-free. The fix is to either: (a) roll the pre-tax IRA balance into your current employer's 401(k), since 401(k) balances are not part of the pro-rata calculation; or (b) pay the tax and convert it all in years your bracket is favourable.

Mega-Backdoor Roth, the bonus version

If your employer's 401(k) plan allows after-tax contributions beyond the $23,500 employee limit and supports in-service withdrawals or in-plan Roth conversions, you can layer the Mega-Backdoor Roth on top of the regular Backdoor. This route can funnel up to $46,500 of additional after-tax money into Roth space each year (the gap between $23,500 + employer match and the $70,000 total cap).

Roughly 15% of 401(k) plans support the full Mega-Backdoor mechanics in 2026. Check your Summary Plan Description for 'after-tax contributions' and either 'in-plan Roth rollovers' or 'in-service distributions.' If your plan supports it and you can afford to fund it, this is the largest legal Roth space available in the U.S. tax code.

Common Backdoor Roth mistakes

• Skipping Form 8606, the IRS will eventually tax the same dollars twice without it.
• Doing the contribution and conversion in different tax years, fine, but creates messy reporting.
• Ignoring the pro-rata rule on existing rollover IRAs, turns a tax-free conversion into a partially taxable event.
• Investing the non-deductible Traditional contribution before converting, any gains become taxable on conversion.
• Forgetting to repeat every January, the Backdoor is an annual ritual.

Step-by-step: the cleanest backdoor in 2026

1. Open a Traditional IRA at the same brokerage as your Roth IRA (Fidelity, Schwab and Vanguard all support this with no fees).
2. Contribute up to $7,000 ($8,000 if 50+) to the Traditional IRA. Mark the contribution as non-deductible if your income exceeds the deduction limit.
3. Wait at least one business day for the funds to settle. Do not invest yet, leave it in the cash sweep.
4. Convert the entire balance to your Roth IRA. Use the brokerage's online conversion tool; no taxes are owed because you converted only post-tax dollars.
5. When you file taxes, complete IRS Form 8606 to report both the non-deductible contribution and the conversion. Skip this and the IRS will tax your conversion twice, once now and again at withdrawal.

The pro-rata rule, with worked numbers

The pro-rata rule is the single biggest landmine in the Backdoor Roth. The IRS treats all of your Traditional, SEP, and SIMPLE IRA balances as one pool when calculating the taxable portion of a conversion. If you have $93,000 of pre-tax money in a rollover IRA from an old 401(k) and contribute $7,000 non-deductible, only 7% of any conversion is tax-free, the other 93% is taxable income.

The fix is to roll the pre-tax IRA balance into your current employer's 401(k) before the conversion (most plans allow this). Once your IRA pre-tax balance is zero on December 31 of the conversion year, the Backdoor Roth converts cleanly with zero tax. Confirm the rollover is complete before December 31, partial-year balances still count.

Mega Backdoor Roth: the larger sibling

The Mega Backdoor Roth uses 401(k) after-tax contributions (separate from Roth 401(k) contributions) plus an in-plan Roth conversion or in-service distribution. The combined 415(c) limit in 2026 is $70,000, so a worker who maxes the $23,500 employee deferral and gets, say, $10,000 of employer match has up to $36,500 of after-tax space. That entire amount can be converted to Roth annually, far more than the $7,000 Backdoor Roth ceiling.

Not every plan supports it. You need both 'after-tax contributions' (not Roth, not Traditional, the third bucket) and either in-plan Roth conversion or in-service distribution. Check with your plan administrator. Tech, finance and consulting employers commonly offer it; smaller companies often do not.

Year-end checklist to keep the Backdoor clean

• Verify Traditional IRA balance is $0 on December 31, including SEP and SIMPLE IRAs (the pro-rata rule lumps them all together).
• Roll any pre-tax IRA into your current 401(k) before December if needed; confirm receipt before year-end.
• Complete the contribution and conversion in the same brokerage and within a few days of each other to minimise growth on the non-deductible contribution.
• File IRS Form 8606 with your tax return to establish basis, without it, the IRS will tax the conversion as if it were pre-tax money.
• Repeat the same workflow each January, Backdoor Roth is an annual habit, not a one-time event.