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

RMD aggregation rules let you add up required minimum distributions across certain similar retirement accounts and take the combined total from just one of them, but the shortcut only works within defined groups: all your Traditional, SEP, and SIMPLE IRAs form one pool; your 403(b) accounts form another; and every 401(k) or 457(b) you own has to settle its own RMD on its own. You can never use a withdrawal from an IRA to cover an employer plan’s RMD, or the reverse.¹

Combining RMDs Across Your IRAs

Traditional IRAs, SEP IRAs, and SIMPLE IRAs all sit in the same aggregation group. You calculate the RMD for each account separately, using that account’s December 31 prior-year balance divided by the appropriate life expectancy factor. Then you add the individual amounts together to get one total. You can withdraw that total from any single IRA or split it across several of them in any proportion you want.¹

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 the IRA holding your lowest-performing investments, or from the one with the most accessible cash, and leave the other two accounts untouched. That flexibility is genuinely useful for tax planning. You can liquidate holdings strategically instead of being forced to sell in every account.

Because SEP and SIMPLE IRAs share the pool, an old SIMPLE IRA from a former employer can satisfy part or all of the RMD you owe on your personal Traditional IRA, or vice versa.²

403(b) Plans Aggregate With Other 403(b) Plans

The 403(b) is the only employer-sponsored plan that allows aggregation. If you hold multiple 403(b) accounts from different employers, calculate each account’s RMD separately, add them together, and take the total from any one or any combination of those 403(b) accounts.¹ The mechanics mirror the IRA rule.

The group is sealed off, though. A 403(b) withdrawal cannot cover an IRA RMD, and an IRA withdrawal cannot cover a 403(b) RMD. Each group stays in its own lane.

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

Every 401(k) stands by itself. If you have two 401(k) accounts from former employers, each one’s RMD must be calculated and withdrawn from that specific plan.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.² This is where people get into trouble. It’s easy to assume that because IRA aggregation is so flexible, employer plans work the same way. They don’t.

If a single 401(k) has multiple sub-accounts or investment options inside it, those sub-accounts aren’t treated as separate plans. The plan calculates one RMD based on the total balance. Which sub-account the distribution comes from is governed by the plan document, not by aggregation rules.

The simplest way to keep the categories straight: an old 401(k) from a previous employer requires its own withdrawal from that specific 401(k), full stop. Rolling several old 401(k)s into a single IRA before you reach RMD age is one way to collapse the problem, because once the money is in an IRA it joins the aggregated IRA pool.

What Never Aggregates

A few boundaries catch people out, so it helps to name them directly.

IRAs and employer plans never mix. Pulling extra from your Traditional IRA doesn’t cover a shortfall in your 401(k) or 403(b), no matter how the math works out.¹

Roth IRAs are not in the pool. Roth IRAs are not subject to RMDs during the original owner’s lifetime. You never include them when calculating your aggregated IRA RMD, and you cannot use a Roth IRA withdrawal to satisfy a Traditional IRA’s obligation. Designated Roth accounts inside employer plans, like a Roth 401(k) or Roth 403(b), are also exempt from lifetime RMDs starting in 2024 under Section 325 of the SECURE 2.0 Act.²

Inherited accounts don’t mix with your own. If you inherit an IRA, you cannot combine that inherited RMD with the RMDs from your own personal IRAs, even though both are Traditional IRAs. An inherited IRA is a separate animal.³

Inherited accounts from different people don’t mix with each other. 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

The Narrow Aggregation Rule for Inherited Accounts

Inherited accounts can aggregate in one specific situation: multiple accounts of the same type inherited from the same person. If your father left you two separate Traditional IRAs, you can add those inherited RMDs together and withdraw the total from either inherited account.³ The accounts have to be the same type and from the same decedent for this to work.

This matters more now that annual distributions are back in play. Most non-spouse beneficiaries who inherited accounts after 2019 are subject to the SECURE Act’s 10-year rule, and if the original owner had already reached their required beginning date, the IRS final regulations require the beneficiary to take annual distributions in years one through nine, then empty the account in year ten.⁴ The IRS waived penalties for missed annual distributions under the 10-year rule from 2021 through 2024, but those waivers have expired.⁵ Starting in 2025, those annual RMDs are enforced where applicable, and the same-decedent, same-type aggregation rule is how beneficiaries with multiple inherited IRAs manage the paperwork.

Spouses have an extra option. A surviving spouse can roll an inherited IRA into their own IRA, which converts it from an inherited account to a personal account. Once rolled over, the funds follow the surviving spouse’s RMD schedule and fully aggregate with their other IRAs.³ A surviving spouse who instead chooses to remain a beneficiary keeps the account separate, with no aggregation into personal accounts.

What a Mistake Costs

If you miscount which accounts aggregate and end up short, the IRS charges a 25% excise tax on the shortfall. The rate drops to 10% if you correct the problem within a two-year window. You report the shortfall and the tax on Form 5329, filed with your federal return for the year the RMD was due.²

The classic aggregation mistake is assuming you can cover a 401(k) RMD by taking a larger withdrawal from your IRA. The extra IRA money 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, take the missing distribution from the correct account immediately.

The IRS can waive the penalty entirely if 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 waive 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 only if the request is denied.⁶ Correcting the missed distribution before you file the waiver request generally improves your odds.

1
Internal Revenue Service. RMD Comparison Chart (IRAs vs. Defined Contribution Plans)
2
Internal Revenue Service. Retirement Plan and IRA Required Minimum Distributions FAQs
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. 2025 Instructions for Form 5329 – Additional Taxes on Qualified Plans (Including IRAs) and Other Tax-Favored Accounts