Why should I pay for Medicare Part B when I already have TRICARE?

The dependency people do not expect

A career of TRICARE teaches a reasonable but wrong lesson: that military healthcare stands on its own. At 65 that stops being true. TRICARE For Life is explicitly a second payer. It is designed to sit behind Medicare and pick up what Medicare does not.

That design has a hard consequence. If Medicare Part B is not in force, there is no first payer for TRICARE For Life to sit behind.

Why this catches people who are otherwise careful

The Part B premium is a visible monthly cost, and declining it looks like a straightforward saving — especially to someone who has had comprehensive coverage for decades and has never had a reason to think of TRICARE as conditional on anything.

The bill for that decision does not arrive until the first serious claim.

The penalty is permanent, which is unusual

Most deadlines in a military career cost you an opportunity. This one attaches a recurring charge. The Part B late enrollment penalty is added to your monthly premium and is charged for as long as you have Part B — it is not repaid over a fixed catch-up period and it does not expire.

That is what makes this an irreversible decision rather than a delayed one.

What to do about it

Start three months before the month you turn 65, not in the month itself. The Initial Enrollment Period spans several months either side of your birth month, and starting early leaves room for the DEERS record to catch up.

Then verify the result rather than assuming it: confirm DEERS shows both Part A and Part B, and confirm your TRICARE coverage has actually converted. A coverage change that did not propagate is discovered at the pharmacy counter otherwise.