Avoid These 5 Common Medicare Enrollment Mistakes During Open Enrollment

What to Do After You Enroll in Medicare: Your December Checklist

Annual Enrollment may be over, but your Medicare to-do list isn’t quite finished yet. December is the perfect time to double-check a few key items so you can start the new year confident, covered, and prepared.

Here’s your simple post-enrollment Medicare Checklist.

1. Confirm Your Enrollment & Effective Date

Most Medicare Advantage and Part D plan changes made during Annual Enrollment take effect January 1 (Medicare.gov, 2026).

What to do:

Watch for enrollment confirmation notices from your plan
Verify the plan name, coverage type, and effective date
Make sure your personal information is correct

If something doesn’t match what you selected, addressing it early makes a resolution much easier. Call us as soon as you notice something doesn’t look right.

2. Know When to Expect Your ID Cards

New plan ID cards are typically mailed mid-December through early January, depending on the carrier (Medicare.gov, 2026).

Helpful tips:

Keep your current card until January 1
Bring your new card to your first appointment of the year
If your card hasn’t arrived by late December, your agent can help request a replacement.

Many plans also provide digital ID cards through their member portal.

3. Re-Check Your Pharmacy & Prescriptions

Even after enrolling, it’s smart to do a final review of your prescriptions before January.

Double-Check:

Your pharmacy is still in-network or preferred
Your medications remain on the plan’s formulary
Any prior authorization or step-therapy rules that may apply

Formularies and pharmacy networks can change each year, and confirming now can help avoid delays or unexpected costs in January (CMS, 2026).

4. What To Do If Something Looks Off

If you notice:

A medication missing from your coverage.
Higher than expected copays
A provider list listed as out-of-network
Enrollment details that don’t match what you chose

Don’t wait. Many enrollment issues are easiest to resolve before coverage begins (NCOA, 2025).

5. Remember: You Still Have Options After January

If your plan doesn’t work as expected once coverage starts, you’re not locked in.

The Medicare Open Enrollment Period (OEPI) runs from January 1 through March 31 each year. During this time, eligible members may:

Switch Medicare Advantage Plans
Return to Original Medicare
Add or change a Part D prescription drug plan

This period allows you to adjust your coverage based on real-world experience (Medicare.gov, 2026).

How Harbor Health Can Help

At Harbor Health Insurance Services, our support doesn’t stop after enrollment. We help you:

Review confirmation notices and plan documents
Check prescriptions and pharmacy coverage
Understand next steps and timelines
Identify issues early
Know your options moving into the new year

From Our Team At Harbor Health Insurance Services

As we wrap up the year, we want to wish you and your family a very Happy Holidays. We’re grateful to support you and are here if you have questions as you head into the new year.

References:

Medicare.gov. (2026). Your Medicare coverage options & enrollment timelines

Centers for Medicare & Medicaid Services (CMS). (2026). Medicare Advantage and Part D program guidance.

National Council on Aging (NCOA). (2025). Understanding Medicare enrollment and plan changes.

Medicare Disclaimer: We do not offer every plan available in your area. Any information we provide is limited to those plans we do offer in your area. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options.