Lesson 14 of 15
Common mistakes to avoid
Last reviewed: January 2026· Next scheduled review: January 2027
Quick answer
The top mistakes are: declining Part B (losing TFL), enrolling in Part D (disrupting TRICARE Pharmacy), assuming MTF access continues, missing the Initial Enrollment Period, and choosing a Medicare Advantage plan without checking whether your doctors are in network.
Key takeaways
- Declining Part B = losing TFL. Permanent penalty.
- Enrolling in Part D is usually wrong for TFL beneficiaries.
- Don't assume your MTF doctor will still see you.
- Don't choose an MA plan in a hurry — check the network and formulary first.
Detailed explanation
The big five
- Declining Part B. You lose TFL and pay a permanent late penalty if you reverse course.
- Enrolling in Medicare Part D. TRICARE Pharmacy is your drug coverage. Part D layered on top causes problems.
- Counting on the MTF. Space-available is not a healthcare plan.
- Missing your IEP. The 7-month window is firm. Mark it on the calendar.
- Picking MA on the brochure. Confirm doctors, formulary, and travel rules before enrolling.
Smaller but expensive
- Forgetting to update DEERS when your address changes.
- Not bringing both cards to appointments.
- Assuming dental and vision are covered.
Frequently asked questions
What's the single most important thing to get right?
Enroll in Medicare Part B during your Initial Enrollment Period. Everything else follows from that.
Official government resources
Official Medicare and TRICARE publications are the definitive source. This page is an independent educational summary; always confirm specifics against the resources above.