RMD Aggregation Rules: IRAs, 403(b)s, and 401(k)s

RMD aggregation rules let you calculate your required minimum distribution for each retirement account, then take the combined total from whichever account you choose — but only within specific groups. All your Traditional, SEP, and SIMPLE IRAs share one aggregation pool. Multiple 403(b) accounts share another. Every 401(k), 457(b), and other defined contribution plan stands on its own, and you can never use an IRA withdrawal to satisfy an employer-plan RMD or the other way around. Getting the grouping wrong triggers a 25% excise tax on whatever you should have withdrawn but didn’t.¹

IRAs: One Big Aggregation Pool

Traditional IRAs, SEP IRAs, and SIMPLE IRAs all belong to the same group. You calculate the RMD for each account separately, using each account’s December 31 prior-year balance divided by the appropriate life expectancy factor from IRS Publication 590-B. Then you add those individual amounts together for one total. You can withdraw that total from any single IRA or split it across several however you like.²

Say you have three Traditional IRAs with individual RMDs of $4,000, $3,000, and $2,500. Your total obligation is $9,500. You could pull the entire $9,500 from whichever IRA has the lowest-performing investments or the most accessible cash, and leave the other two accounts untouched. The flexibility is genuinely useful for tax planning: you can liquidate holdings strategically rather than being forced to sell in every account.

The IRS treats SEP and SIMPLE IRAs as part of the same pool as Traditional IRAs for RMD purposes.¹ So if you have a Traditional IRA and an old SIMPLE IRA from a former employer, you can satisfy the combined obligation from either one.

403(b) Plans: The Employer-Plan Exception

The 403(b) is the only employer-sponsored plan that allows aggregation. If you hold multiple 403(b) accounts from different employers, you calculate each account’s RMD separately, add them together, and take the total from any one or combination of those 403(b) accounts.² The mechanics mirror the IRA rule.

You still cannot use a 403(b) withdrawal to cover an IRA RMD or vice versa. The two groups stay in their own lanes.

401(k), 457(b), and Other Defined Contribution Plans: Each Stands Alone

Every 401(k) is treated as its own plan. If you have two 401(k) accounts from former employers, each one’s RMD must be calculated and withdrawn from that specific plan. The same applies to governmental 457(b) plans and profit-sharing plans.¹ This is where people get tripped up. It’s tempting to assume that because IRA aggregation is so flexible, employer plans work the same way. They don’t.

Pulling extra from your Traditional IRA doesn’t cover a shortfall in your 401(k), no matter how the math works out.² The extra IRA withdrawal is just an extra IRA withdrawal.

Sub-accounts inside a single 401(k) aren’t separate plans. If your plan has multiple investment options or recordkeeping buckets, the plan calculates one RMD based on your total balance, and the plan document governs which sub-account the distribution actually comes from.

Roth Accounts Sit Outside

Roth IRAs are not subject to RMDs during the original owner’s lifetime. You never include them in your aggregated IRA RMD, and you cannot use a Roth IRA withdrawal to satisfy a Traditional IRA’s RMD.¹

Designated Roth accounts inside employer plans, like a Roth 401(k) or Roth 403(b), are also exempt from RMDs during the owner’s lifetime starting in 2024 under Section 325 of the SECURE 2.0 Act.¹ Before this change, Roth 401(k) participants either took RMDs or rolled the money into a Roth IRA to avoid them. That workaround is no longer necessary.

Inherited Accounts Follow Their Own Rules

Inherited retirement accounts are walled off from your own, and inherited accounts from different people are walled off from each other. You cannot combine an inherited IRA’s RMD with the RMD from an IRA you own personally, even when both are the same account type.³

When you inherit accounts from different people, each decedent’s accounts stay in their own silo. If you inherited a Traditional IRA from your mother and another from your uncle, you calculate and take two separate RMDs. You cannot pull extra from one to cover the other.³

Aggregation is only allowed when you inherit multiple accounts of the same type from the same person. If your father left you two separate Traditional IRAs, you can add those RMDs together and withdraw the total from either inherited account. Same type, same decedent — otherwise, no combining.

Annual RMDs Under the 10-Year Rule

Most non-spouse beneficiaries who inherited accounts after 2019 are subject to the SECURE Act’s 10-year rule, which requires the entire inherited account to be emptied by the end of the tenth year after the owner’s death.⁴ Whether you also owe annual RMDs during that window depends on whether the original owner had already started taking RMDs before they died.

If the original owner died on or after their required beginning date, the IRS final regulations require beneficiaries to take annual distributions during years one through nine and empty the account in year ten. If the owner died before their required beginning date, no annual RMDs are required during the 10-year period, though the account still must be drained by the end of year ten. The IRS waived penalties for missed annual distributions under the 10-year rule for 2021 through 2024 while the regulations were finalized, but those waivers have expired.⁵ Starting in 2025, annual RMDs during the 10-year window are enforced where applicable.

Aggregation works the same way inside these inherited accounts. If you inherited two Traditional IRAs from the same parent and both require annual distributions, you can aggregate those amounts and take the total from either one.

Spousal Beneficiaries

A surviving spouse has options no other beneficiary gets. The most common move is to roll the inherited account into your own IRA, which converts it from an inherited account into your personal account. After the rollover, the funds follow your own RMD schedule and fully aggregate with your other IRAs.³

A surviving spouse can also choose to remain a beneficiary. The inherited account then stays separate and follows its own distribution rules, not aggregated with the spouse’s personal accounts. Rolling over is simpler for most people, but keeping the account separate can make sense if the surviving spouse is younger than 59½ and needs access without the 10% early withdrawal penalty.

Calculating Each RMD Before You Aggregate

Every RMD starts with the same formula: take the account balance as of December 31 of the prior year and divide it by a life expectancy factor from the IRS tables.¹

Most account owners use the Uniform Lifetime Table, based on your age in the current distribution year. One exception: if your sole beneficiary is your spouse and your spouse is more than 10 years younger than you, you use the Joint Life and Last Survivor Expectancy Table instead. That table produces a longer life expectancy factor and a smaller RMD.⁶

Once you have each account’s RMD, apply the aggregation groups: add all IRA RMDs together, add all 403(b) RMDs together, and take each 401(k) RMD from that specific plan. All withdrawals must be completed by December 31 of the distribution year.

Penalties for Aggregation Mistakes

If you don’t withdraw the full RMD by the deadline, the IRS charges a 25% excise tax on the shortfall. That drops to 10% if you correct the mistake within a two-year correction window. You report the shortfall and the tax on Form 5329, filed with your federal return for the year the RMD was due.¹

The IRS can waive the penalty entirely if you show the shortfall was due to a reasonable error and you’ve taken steps to fix it. To request a waiver, attach a written explanation to Form 5329 describing what went wrong, enter “RC” and the shortfall amount you’re asking to have waived on the dotted line next to line 54, and calculate any remaining tax due on line 55. The IRS reviews the explanation and notifies you if the request is denied.⁷

The classic aggregation error is assuming you can cover a 401(k) RMD by withdrawing more from your IRA. That extra IRA withdrawal doesn’t count toward the 401(k) obligation, so you end up with a shortfall in one plan and an unnecessary extra withdrawal from the other. If you catch the mistake before the IRS does, take the missing distribution immediately and use the Form 5329 waiver process. The IRS is generally receptive to waiver requests when the taxpayer has already corrected the problem.

1
Internal Revenue Service. Retirement Plan and IRA Required Minimum Distributions FAQs
2
Internal Revenue Service. RMD Comparison Chart (IRAs vs. Defined Contribution Plans)
3
Internal Revenue Service. Publication 590-B (2025), Distributions from Individual Retirement Arrangements (IRAs)
4
Internal Revenue Service. Retirement Topics – Beneficiary
5
Internal Revenue Service. Notice 2024-35, Certain Required Minimum Distributions for 2024
6
Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs)
7
Internal Revenue Service. 2025 Instructions for Form 5329 – Additional Taxes on Qualified Plans (Including IRAs) and Other Tax-Favored Accounts