He Has Four IRAs and One RMD. Every December He Takes the Whole Thing From a Single Account and Never Touches the Other Three. The IRS Wrote the Rule Itself, and It Doesn’t Work for 401(k)s

If you own more than one traditional IRA, the IRS gives you a piece of flexibility almost nobody uses on purpose: you can add up your required minimum distributions across every IRA you own and pull the entire total from a single account. The other IRAs can sit untouched all year; this is known as the IRA RMD aggregation rule, and it exists for a reason. It also stops cold at the edge of your IRAs, which is where the expensive mistakes happen.

How the Two Step Actually Works

The mechanics aren’t what most people assume. It starts by calculating a required distribution separately for each traditional IRA, using that account’s December 31 prior year-end balance and the IRS life expectancy factor. Then you add those numbers together. That total is your obligation, and you can satisfy it from any one IRA, or any combination, in any proportion. The math is per account, but withdrawals are flexible. Miss that distinction and you either overpay or, worse, undershoot.

Regulation That Grants It

The authority is Treasury Regulation §1.408-8, which governs distributions from IRAs, together with IRS Publication 590-B, which restates the aggregation rule in plain English for taxpayers. Both make clear the rule applies to traditional IRAs, SEP IRAs, and SIMPLE IRAs held by the same owner. The IRS wrote it this way.

Why This Is Real Flexibility for Retirees

The practical value shows up at year-end. You can leave a concentrated stock position alone instead of selling it into a bad market. You can protect an illiquid holding, a private fund interest, or an annuity inside an IRA and pull the whole obligation from a cash-heavy account instead. You can preserve a small legacy IRA you never want to touch. You also compress the year-end paperwork into a single transaction with a single custodian. For retirees, this is one of the few places the rules bend in your favor.

Where the Rule Stops Cold

• 401(k) plans do not aggregate, as each 401(k) must pay its own required amount from its own assets, and a 401(k) obligation can never be satisfied from an IRA or from a different 401(k). This is the single most expensive misunderstanding in the area, and it is the one people make when they assume “retirement account” is one category.
• 403(b) plans aggregate only among other 403(b) plans owned by the same participant. They do not combine with IRAs or 401(k)s. That is a third, separate pool with its own math.
• Inherited IRAs aggregate only with other inherited IRAs received from the same decedent, and only within the same type (traditional with traditional, Roth with Roth). They never combine with your own IRAs. Someone holding both is running two independent calculations. Accounts belonging to a spouse never aggregate with yours, because retirement accounts are individual by definition.
• Roth IRAs owe no lifetime RMD to the original owner, so they do not enter the calculation at all. An inherited Roth is different: the beneficiary faces distribution requirements and must meet them within the inherited-Roth pool.

Penalty for Crossing a Boundary

Under SECURE 2.0, a missed RMD triggers an excise tax of 25% of the shortfall, reduced to 10% if you correct it within a two-year window. You request the reduction and any reasonable-cause waiver on Form 5329. The most common way to trigger it is exactly the assumption above: pulling a 401(k) obligation out of an IRA and thinking the total covered both, which is, in fairness, a common mistake.

Inventory to Build Before December

Start by listing every retirement account you own by type. Group them into pools: traditional IRAs together, each 401(k) on its own line, 403(b)s together, inherited IRAs by decedent. Calculate within each pool using the prior year-end balance. Satisfy each pool independently by December 31. If this is your first RMD year, you have until April 1 of the following year for that first distribution only, and taking both in the same year stacks the income (the smarter move is shrinking the balance years before the first required withdrawal ever lands, which we walked through in a free guide on defusing the first-year tax bomb).

You can’t roll over an RMD, and you can’t convert it to a Roth, no matter how much readers try. If an old employer plan is sitting somewhere you forgot about, it has its own obligation. Rolling it into an IRA before your required beginning date collapses the pools and makes the aggregation rule work for you.

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