Do I need a Part D drug plan?

No. And this is one of the most common mistakes.

The TRICARE Pharmacy Program — administered by Express Scripts — is certified by CMS as creditable coverage. That means:

• You're not subject to a Part D late-enrollment penalty for skipping it.
• You don't need Part D to have prescription coverage.
• Enrolling in a standalone Part D plan can interfere with TRICARE Pharmacy claims processing.

You have four channels for prescriptions through TRICARE:

1. Military pharmacy — free, lowest cost.
2. TRICARE Home Delivery — cheapest mail-order for 90-day fills.
3. TRICARE retail network (e.g., CVS, Walgreens) — small copay.
4. Non-network pharmacy — highest cost, generally avoid.

The one exception: if you join a Medicare Advantage plan that includes Part D (MA-PD), you'll have both. You can choose whichever fills are cheaper. This is fine — the issue is enrolling in a standalone Part D plan on top of TFL.