What Happens If You Enroll in More Than One Medicare Part D Plan?

Created by Melinda Caughill, Modified on Thu, 4 Dec, 2025 at 11:44 AM by Melinda Caughill

Medicare does not allow you to be enrolled in multiple Part D plans at the same time. If you enroll in more than one plan during Open Enrollment, Medicare automatically decides which one becomes active.

In most cases, the rule Medicare uses is simple:
The last Part D plan you enroll in becomes your official plan for January 1.

Each new enrollment cancels the previous one. This is not a HeyMOE rule — it is built into Medicare’s enrollment system.

The Official Medicare Rule (From CMS)

This rule comes from the federal agency that runs Medicare: the Centers for Medicare & Medicaid Services (CMS).

Source: CMS — CY 2026 Medicare Advantage and Part D Enrollment and Disenrollment Guidance

Section 70.1: Multiple Transactions

Official CMS language:

“Generally, the last enrollment request the individual makes during an enrollment period will be accepted as the plan into which the individual intends to enroll.

If an individual elects more than one plan for the same effective date and with the same application date, the first transaction successfully processed by CMS will take effect.

When simultaneous enrollment in certain MA plan types and a separate PDP is permitted, CMS systems will accept both enrollments.”

What This Means in Real Life

In almost all situations:

The most recent enrollment becomes your Part D plan.
You will never have two Part D plans at once.
You will not be billed twice.
There is no penalty just for enrolling more than once.

Important exception: If you enroll in two plans on the same day with the same effective date, Medicare does not use “last click.” Instead, the plan CMS processes first in its system will take effect.

This is why enrolling multiple times on the same day can sometimes result in the “wrong” plan winning.

How to Check Which Plan You’re Actually In

To see which plan Medicare has on file for you:

Go to Medicare.gov
Sign in to your account
Click My Coverage

The plan listed there is your official Part D plan for January 1.

Bottom Line

Medicare enforces a one-plan rule for Part D. If you enroll more than once, the system chooses based on timing and processing order.

HeyMOE Tip:

In almost every case: the last plan you enroll in is the plan you get.