Backdoor Roth Deadline: April 15 vs. December 31?

The backdoor Roth IRA has three dates that actually matter. Your nondeductible Traditional IRA contribution has to be in the account by April 15 of the year after the tax year you’re targeting — so April 15, 2026, for a 2025 contribution. The Roth conversion itself has no fixed deadline, and it gets reported in whichever calendar year you complete it, not the year of the contribution. And December 31 of the conversion year is the date the IRS uses to snapshot every Traditional, SEP, and SIMPLE IRA you own to decide how much of the conversion is taxable.

The April 15 Contribution Deadline

The first step of the strategy is a nondeductible contribution to a Traditional IRA. You can make that contribution anytime from January 1 of the tax year through April 15 of the following year. For the 2025 tax year, the IRS has confirmed the deadline is Wednesday, April 15, 2026.¹ When the deposit is made in the first few months of 2026, you have to tell your custodian it is “for” 2025.

Here is where people get burned: filing a tax extension does not extend the IRA contribution deadline. If you file Form 4868 and push your return to October 15, your contribution deadline is still April 15.² The extension buys you time on paperwork, not on deposits.

That contribution creates your “basis” in the Traditional IRA — the after-tax dollars the IRS will not tax again when you convert. Documenting the basis correctly is what makes the whole strategy work.

The Conversion Step Has No Fixed Deadline

Once the nondeductible contribution is sitting in your Traditional IRA, you convert it to a Roth. No IRS deadline governs when you have to do this. You can convert the same day, a week later, or years later. The conversion is reported in the calendar year you actually complete it, which is not necessarily the tax year of the contribution. A nondeductible contribution made in March 2026 for the 2025 tax year, and converted in April 2026, shows up on your 2026 tax return, not your 2025 return.³

Most experienced advisors recommend converting immediately, ideally the same day. Every day the money sits in the Traditional IRA it can gain or lose value. Gains become taxable at conversion, which defeats the point of trying to move money into a Roth tax-free. Losses leave you with unused basis. A same-day conversion out of a settlement or money market fund keeps the arithmetic clean: contribute $7,500, convert $7,500, taxable amount zero.

One source of confusion worth clearing up: the 60-day indirect rollover rule does not apply here. That rule governs distribution checks moving between IRAs. A Roth conversion is a separate transaction under the tax code, usually a direct trustee-to-trustee transfer or a redesignation inside the same brokerage, and the 60-day clock is not part of it.

Why December 31 Matters

The date that quietly controls whether your conversion is tax-free or partly taxable is December 31 of the conversion year. That is the day the IRS uses to add up every Traditional, SEP, and SIMPLE IRA you own for purposes of the pro-rata rule. Line 6 of Form 8606 asks for the total value of all your Traditional IRAs as of December 31.³

The pro-rata rule does not let you cherry-pick which dollars you are converting. Every dollar you convert carries a proportional share of the pre-tax and after-tax money across all your non-Roth IRAs. If your December 31 balance includes pre-tax money from old deductible contributions, a rollover from a former employer’s 401(k), or a SEP IRA funded by your business, a slice of your conversion will be taxable.

The numbers get ugly quickly. Say you have $93,000 of pre-tax money in a rollover IRA and you make a $7,000 nondeductible contribution for the backdoor Roth. Your total IRA balance is $100,000, and only 7% of it is after-tax. Convert $7,000 and roughly $6,510 of that conversion is taxable. The strategy runs cleanly only if your total non-Roth IRA balance on December 31 is zero, or close to it, aside from the nondeductible contribution you are converting.

The standard workaround is moving all pre-tax IRA money into an employer-sponsored plan such as a 401(k) before December 31 of the conversion year. Most 401(k) plans accept incoming rollovers of pre-tax IRA money, though you should confirm with your plan administrator. This reverse rollover zeros out the pre-tax IRA balance and leaves only the nondeductible contribution behind, which then converts entirely tax-free.

Form 8606 and Its Filing Deadline

The IRS assumes every dollar in your Traditional IRA is pre-tax unless you prove otherwise. You prove it by filing Form 8606, Nondeductible IRAs, with your annual tax return.³ Part I records the nondeductible contribution and locks in your basis. Part II records the conversion and calculates the taxable portion. Because the contribution and conversion can fall in different tax years, you might file Part I with one year’s return and Part II with the next.

The Form 8606 deadline follows your tax return deadline: April 15, or October 15 if you filed an extension. If you would not otherwise be required to file a return, you can send Form 8606 by itself. Sign it, add your address, and mail it to the IRS service center where you would normally file.³

Skip the form and the damage compounds. The statutory penalty for failing to file Form 8606 is $50, and overstating nondeductible contributions carries a $100 penalty per occurrence.⁴ Those numbers are small; the real cost is that without a documented basis, the IRS treats the entire conversion as taxable income and effectively taxes money you already paid taxes on once.

What Happens If You Miss the Contribution Deadline

A contribution that lands after April 15 counts as an excess contribution for the prior tax year. The IRS imposes a 6% excise tax on excess contributions, and it recurs every year the excess stays in the account.⁵ On a $7,500 contribution, that is $450 a year until it is fixed.

Two ways out. You can withdraw the excess contribution plus any earnings on it by the tax-filing deadline, including extensions, which means as late as October 15 if you filed Form 4868.² The withdrawn earnings are taxable and may face the 10% early withdrawal penalty. Or you can redesignate the late contribution as applying to the current tax year, as long as you have not already maxed out the current year’s limit.

Conversions Are Permanent, Contributions Are Not

Before 2018, a Roth conversion could be undone by recharacterizing it back to a Traditional IRA. The Tax Cuts and Jobs Act eliminated that. Any Roth conversion completed on or after January 1, 2018, cannot be reversed.⁶ Once you convert, it is done.

Contributions are different. If you made a direct Roth IRA contribution early in the year and then discover your income disqualifies you, you can recharacterize that contribution as a Traditional IRA contribution by the tax-filing deadline, including extensions — October 15, 2026, for a 2025 contribution if you filed an extension.⁶ After recharacterizing, you can convert to Roth and end up in the same place as a planned backdoor, without an excess contribution penalty.

The Five-Year Clock on Converted Amounts

One deadline that runs in the other direction is worth knowing about before you withdraw anything. Each Roth conversion starts its own five-year clock. If you pull converted amounts out within five taxable years of the conversion and you are under 59½, the IRS can apply a 10% early withdrawal penalty, but only on the portion that was taxable at conversion.⁷

For a cleanly executed backdoor Roth, this is mostly academic. If you contributed $7,500 of nondeductible money, converted $7,500 the same day with zero gains, and had no pre-tax IRA balances, the taxable portion at conversion was zero. Ten percent of zero is zero. The five-year rule bites only when a meaningful portion of the conversion was taxable, which typically means gains accrued before you converted or the pro-rata rule pulled pre-tax dollars into the conversion.

1
Internal Revenue Service. IRS Announces First Day of 2026 Filing Season
2
Internal Revenue Service. IRA Year-End Reminders
3
Internal Revenue Service. Instructions for Form 8606 (2025)
4
Office of the Law Revision Counsel. 26 U.S. Code 6693 – Failure to Provide Reports on Certain Tax-Favored Accounts or Annuities
5
Office of the Law Revision Counsel. 26 USC 4973 – Tax on Excess Contributions to Certain Tax-Favored Accounts and Annuities
6
Internal Revenue Service. Retirement Plans FAQs Regarding IRAs
7
Office of the Law Revision Counsel. 26 U.S. Code 408A – Roth IRAs