Mega Backdoor Roth 2026: Limit, How It Works and Rules

Two things have to be true in your plan, and the plan, not the law, decides both:

• It accepts after-tax contributions. The IRS contributions page defines them as contributions from compensation (other than Roth contributions) that you must include in income, and says: "If a plan allows after-tax contributions, they are not excluded from income and an employee cannot deduct them on his or her tax return."
• It lets you move them to Roth. There are two routes in the IRS notices. A plan with a designated Roth account can allow an in-plan Roth rollover to that account (Notice 2013-74, which says an amount must be vested to be eligible). Or the plan can pay the after-tax amounts out to you or to another destination, such as a Roth IRA (Notice 2014-54).

Ask your plan administrator whether the plan takes after-tax contributions and which of the two moves it permits, and how often.

Your after-tax contributions were already included in your income, so moving them to Roth is not taxed again. What gets taxed is the pretax part of what you move. Notice 2014-54 sets the allocation rules for a plan that pays out to more than one destination:

• All disbursements scheduled at the same time are treated as a single distribution, even if you direct them to several destinations.
• The pretax amount is assigned first to the part that is directly rolled over, so you can choose which rollover receives it. In the notice's Example 4, an $80,000 direct rollover to a traditional IRA takes the pretax amount and the $20,000 rolled over to a Roth IRA consists entirely of after-tax amounts.
• The allocation rules apply to distributions made on or after January 1, 2015.

Example 4 builds on Example 1, and that example starts from the pro rata rule: under section 72(e)(8), each distribution from an account that holds both after-tax and pretax amounts includes a pro rata share of both. In Example 1 an account of $200,000 pretax and $50,000 after-tax pays a $100,000 distribution that includes $80,000 of pretax amounts, so you cannot count on taking out only the after-tax part of a partial withdrawal. The notice divides each distribution into the pretax amount and the after-tax amount. Earnings on after-tax contributions are not after-tax contributions, so we read them as part of the pretax amount; the notice does not give a separate rule for them. Notice 2010-84 says the taxable amount of an in-plan Roth rollover is includible in gross income in the taxable year in which the distribution occurs, and Publication 590-A says amounts converted from a traditional IRA to a Roth IRA are included in income in the year of the conversion. Ask your plan administrator and a tax professional before moving money; this page does not give tax advice.

A backdoor Roth IRA goes through an IRA, so the backdoor Roth limit 2026 is the IRA contribution limit: $7,500, or $8,600 if you are 50 or older ($1,100 IRA catch-up). A mega backdoor Roth goes through your 401(k), so the cap is the plan limit ($72,000) less deferrals and employer contributions, which can be several times larger. The two are separate: one runs in an IRA and the other in an employer plan.

The IRS does not use the phrase "backdoor Roth" either. See what the IRS says about backdoor Roth IRA steps: nondeductible contributions, conversions and Form 8606.

As of Nov. 7, 2026, the IRS had not published the 2027 limits. The IRS announced the 2026 limits on November 13, 2025, so the 2027 notice is expected in mid-November. We do not estimate the amounts; this page will show the IRS figures once the notice is out.

The regular 2027 plan limits are on the 2027 retirement limits page.