What If You Take Less Than Your Full RMD by Mistake?
Not every RMD mistake means nothing came out at all. Sometimes a withdrawal happens on schedule, but the amount is smaller than what was actually required — an easy error to make when the calculation relies on the wrong balance or the wrong factor.
The short answer
A partial or shortfall RMD occurs when some money is withdrawn by the deadline, but less than the full required amount. The excise tax penalty that can apply to a missed RMD applies specifically to the unmet portion — the gap between what should have gone out and what actually did — not to the entire distribution. Correcting it generally means withdrawing the difference as soon as the error is caught and, in some cases, requesting that the penalty be reduced or waived.
How a shortfall typically happens
Miscalculating an RMD is more common than it might seem, since the amount depends on the account balance at a specific prior date and a life-expectancy factor pulled from a published table. A stale balance, a factor pulled from the wrong table, or simply forgetting that multiple accounts sometimes need to be combined before the total is divided up can all produce a number that’s too low. None of these are exotic mistakes — they’re the kind that happen when someone is doing the math manually or working from outdated information.
Why the penalty only touches the gap
It’s a common misconception that any RMD error triggers a penalty on the whole distribution. In practice, the potential excise tax penalty applies only to the difference between the required amount and what was actually withdrawn. Someone who was supposed to withdraw a certain amount and took most of it, but not quite all, would generally only face exposure on the remaining sliver — a meaningfully smaller number than the full RMD, though still worth fixing promptly.
Fixing the shortfall
Once a shortfall is discovered, the general approach is to withdraw the missing amount right away, even if it falls in a later tax year than originally intended. Tax rules generally allow the penalty to be reduced or waived when the shortfall is corrected within a defined window and there’s a reasonable explanation, such as relying on incorrect information from an account custodian. This usually involves filing a specific form with the tax return and, in some cases, attaching an explanation of what went wrong and what was done to fix it.
Keeping it from happening again
Because the RMD calculation depends on accurate account balances and the right factor for the account holder’s age, double-checking those two inputs each year — rather than reusing a prior year’s math — is one of the more reliable ways to avoid a shortfall. It’s also worth confirming whether accounts qualify to be combined for a single aggregated withdrawal or need separate calculations, since that distinction is a frequent source of underpayment, particularly for someone managing an inherited account alongside their own.
What to weigh
A shortfall RMD is a narrower, more fixable problem than a fully missed one, since the penalty exposure is limited to the gap rather than the whole amount. Because the calculation inputs, the correction window, and the penalty rules are all set by the government and can change, confirming current details with a custodian or tax professional is generally more reliable than assuming last year’s approach still applies.