Medicare 2026

Working past 65 in Walnut Creek? When to sign up for Medicare

WALNUT CREEK, Calif. — If you're approaching 65 and still clocking in — whether at a job in downtown Walnut Creek, up in Shadelands, or remotely from home — one of the trickiest Medicare questions is simply when to enroll. The answer depends on the size of your employer, how your current coverage works, and a few deadlines that can be costly to miss.

Here's how to think it through.

Start with the size of your employer

The single biggest factor is how many people work at your company. Under Medicare's rules, if your employer has 20 or more employees, the group health plan is generally the primary payer and Medicare is secondary. That means you can usually delay signing up for Part B (which has a monthly premium) without owing a late-enrollment penalty later.

If your employer has fewer than 20 employees, Medicare typically becomes the primary payer at 65. In that case, your group plan may pay little or nothing for services Medicare would have covered — so most people in this situation should enroll in Parts A and B when first eligible.

Not sure which rule applies to you? Ask your HR or benefits office in writing. Walnut Creek workers whose employers are headquartered elsewhere should still ask, since the rule is based on employee count, not location.

What about Part A?

Part A (hospital insurance) is premium-free for most people who've worked and paid Medicare taxes for at least 10 years. Because it usually costs nothing, many people enroll in Part A at 65 even while keeping employer coverage.

There is one important exception: if you contribute to a Health Savings Account (HSA), you must stop HSA contributions once any part of Medicare begins — including Part A. Some workers choose to delay Part A specifically to keep contributing to their HSA. If that's you, talk with your benefits office and a tax advisor before deciding.

The Special Enrollment Period when you retire

When you eventually leave your job or lose employer coverage, Medicare gives you an 8-month Special Enrollment Period (SEP) to sign up for Part B without a late penalty. The clock starts the month after your employment or group coverage ends — whichever comes first.

A common, expensive mistake: assuming COBRA or a retiree plan counts as active employer coverage. It doesn't. Once your job ends, the SEP clock is ticking even if you're still on COBRA.

Don't forget Part D (drug coverage)

If your employer plan includes prescription drug coverage that Medicare considers "creditable" (at least as good as a standard Part D plan), you can delay Part D without penalty. Your plan should send you a Notice of Creditable Coverage each year — keep it. If your coverage isn't creditable, or you go more than 63 days without creditable drug coverage after becoming Medicare-eligible, you could face a lifelong Part D late penalty.

For 2026, Part D has a $2,100 annual out-of-pocket cap on covered drugs and a maximum deductible of $615, per CMS. The old "donut hole" coverage gap was eliminated in 2025, and Medicare's optional Prescription Payment Plan lets you spread drug costs across the year in monthly installments.

What's available locally

Walnut Creek is in Contra Costa County, where a range of Medicare Advantage and stand-alone Part D plans are offered each year. Plan choices and costs change annually, so once you're ready to enroll, compare current-year options on Medicare's Plan Finder at medicare.gov.

Also worth knowing if your income is higher: IRMAA surcharges — extra amounts added to Part B and Part D premiums — begin above $109,000 in income for a single filer in 2026. Social Security uses your tax return from two years earlier to determine this.

Key dates to remember

• Initial Enrollment Period: The 7-month window around your 65th birthday (3 months before, your birthday month, and 3 months after).
• Special Enrollment Period: 8 months after employer coverage ends, for Part B.
• Annual Enrollment Period: October 15 – December 7, to join, switch, or drop Medicare Advantage or Part D plans.
• Medicare Advantage Open Enrollment: January 1 – March 31, for people already in a Medicare Advantage plan who want to switch or return to Original Medicare.