You can easily understand why San Antonio is called Military City USA just by exploring the area a bit. There's Joint Base San Antonio, which includes Fort Sam Houston, Lackland, and Randolph, and many retirees choose to settle down here.

However, in such neighborhoods, a common mistake is often repeated as people approach their 65th birthday. It's about Medicare Part B.

Recently, someone mentioned, "I have TRICARE, so I don't need Medicare, right?" Honestly, I thought similarly at first.

To get straight to the point, that thought is the most dangerous. TRICARE For Life, or TFL, requires you to have both Medicare Part A and Part B to receive benefits.

The official TRICARE guidance states that if you qualify for free Part A, you must also have Part B, regardless of your age or where you live, to maintain TRICARE eligibility. If you need Part B but don't have it, you won't be able to access TRICARE benefits at all.

So, Part B is not optional; it's like a ticket. If you miss it, the moment you turn 65, your existing TRICARE plan ends, and TFL won't kick in to fill that gap.

To simplify the TFL structure: Medicare pays the hospital bills first, and TFL covers the remaining costs.

If a service is covered by both Medicare and TRICARE, your out-of-pocket costs are minimal. This is why military retirees often praise TFL as a great program.

There's no enrollment fee for TFL itself. However, you will need to pay the monthly premium for Part B.

The standard Part B premium announced by CMS for 2026 is $202.90 per month. This is an increase of $17.90 from $185 in 2025, and the annual deductible has risen from $257 to $283.

Keep in mind that if your income exceeds a certain level, an additional premium called IRMAA will apply. When I first saw this number, I felt it was a bit steep to pay over $200 a month.

However, if you delay and don't pay, it will become more expensive. If you could have applied for Part B but didn't, your premium will increase by 10% for each 12-month period you delay, and this surcharge will follow you as long as you maintain Part B.

For example, if you delay for two years, you'll end up paying 20% more than the standard premium for life. A single decision can affect your monthly bills for decades.

The application period is based on the month of your 65th birthday, with three months before and after, totaling seven months for your initial enrollment. You need to apply before your birthday month to have coverage start on the first day of that month.

If you miss this window and don't have a special enrollment reason, you'll have to wait for the general enrollment period from January 1 to March 31 each year. During that time, there may be a gap in your TRICARE coverage.

One case that confuses many is for those who have retired from the military and are receiving employer-based insurance from a private company or government agency.

If you have a group insurance plan based on your current job, you can postpone Part B without penalty. However, during that time, you will use your employer's insurance, and your TRICARE eligibility will be paused.

Once you retire or your employer insurance ends, you must apply for Part B within eight months. Note that COBRA is not considered employer insurance for this purpose.

TRICARE guidance is simpler. If you apply for Part B before losing your employer insurance, TFL will start immediately after your employer insurance ends.

You also need to consider your spouse's situation. If the sponsor is still active duty, the family can maintain TRICARE without Part B, but once the sponsor retires, the situation changes.

TRICARE advises active duty families to apply for Part B before the sponsor retires. It clearly states that if you apply after retirement, there will be a gap in TRICARE coverage.

Even if you are under 65, the same rules apply to retirees and their families who qualify for Medicare Part A due to disability. If you have Part A, you must also have Part B to maintain TRICARE.

On the other hand, if you have TFL, you generally don't need to enroll in Medicare Part D separately. The official guidance states that you can use the TFL pharmacy program and delay Part D enrollment without incurring penalties.

So, what should you do? Here's the order I recommend.

Three months before your 65th birthday, apply for both Part A and Part B through the Social Security website or office. If you're not yet receiving retirement benefits, you won't be automatically enrolled, so you need to do it yourself.

Once you receive your Part B card, check to ensure your DEERS information is updated correctly. If you have employer insurance, make sure to set the start date for Part B to align with your retirement date.

Since the applicable rules may vary based on personal circumstances, be sure to confirm with TRICARE, Social Security, or a retirement specialist before making your final decision.

For me, even if $202 a month feels like a lot, I would never delay Part B. It would be too unfortunate to miss out on TFL benefits earned from years of military service just because of one piece of paperwork.