The rules, by account type
| Account type | Aggregation rule |
|---|---|
| Your own traditional, SEP, and SIMPLE IRAs | Aggregate. Calculate the RMD for each IRA separately, add them up, and withdraw the total from any one (or any combination) of your IRAs. |
| 401(k), 403(b)-style employer plans | 401(k)s: no aggregation. Each plan's RMD must come out of that plan. 403(b)s: aggregate, 403(b) RMDs can be combined and taken from any of your 403(b) accounts. |
| Governmental 457(b) | Generally treated like 401(k)s, plan-by-plan. Confirm with the administrator. |
| Inherited IRAs | Only with IRAs inherited from the same decedent. Inherited from two different people? Two separate RMD calculations, two separate withdrawals, they never combine. And inherited IRAs never aggregate with your own IRAs. |
Why this matters in practice
Example. You're 75 with three accounts: IRA #1 ($200,000), IRA #2 ($100,000), and an old 401(k) ($150,000). Your Uniform Lifetime Table factor at 75 is 24.6.
- IRA #1 RMD: $200,000 ÷ 24.6 ≈ $8,130
- IRA #2 RMD: $100,000 ÷ 24.6 ≈ $4,065
- IRA total: ≈ $12,195, withdrawable from either IRA, e.g. all from IRA #1.
- 401(k) RMD: $150,000 ÷ 24.6 ≈ $6,098, must come out of the 401(k) itself. Taking an extra $6,098 from an IRA does not satisfy it.
The classic mistake. Someone with a 401(k) and an IRA takes their entire combined RMD from the IRA, easy, one withdrawal. The IRA portion is satisfied; the 401(k) portion is missed entirely. Penalty: 25% of the 401(k) shortfall. The IRS does not care that you withdrew "enough in total."
Special situations
- Roth IRAs (your own): no RMDs during your lifetime, so nothing to aggregate.
- Designated Roth accounts in a 401(k): no RMDs since SECURE 2.0 (2024), but the rest of the 401(k) still owes its RMD from the plan.
- Still working: the still-working exception can delay the current employer's plan RMD, which changes the aggregation picture that year. Recheck annually.
- First RMD year: the April 1 extension applies per-account-type on its own schedule, another reason to track each bucket separately.
Disclaimer. Educational purposes only, not tax, legal, or financial advice. Verify with a qualified tax professional. IRS Publication 590-B is the authoritative source.