Medicare 2026

Your Doctor's ACO Notice in 2027: The May 30 Deadline and Your Data-Sharing Choice

If a letter arrives from your doctor's office saying your provider participates in a Medicare "Accountable Care Organization" (ACO), you are not being switched into a new plan, and no one is trying to scam you. Starting in 2027, the way and when you get that notice is changing, and it's worth understanding what it means, what choices you have, and what it does not change about your Medicare.

What an ACO is — and what it isn't

An Accountable Care Organization is a group of doctors, hospitals, and other clinicians who agree to work together and be measured on the quality and cost of care for people with Original Medicare. The Medicare Shared Savings Program is the largest of these arrangements.

Medicare.gov is clear on two important points: ACOs are not Medicare Advantage Plans, and having a provider who participates in an ACO does not change your Original Medicare coverage, your costs, or your rights — including your freedom to visit any provider who accepts Medicare. You are not being enrolled in anything. You are not locked into a network. Your Medicare card still works the same way.

CMS itself has noted that the ACO notice has sometimes caused confusion — some people have assumed the letter was a fraud attempt, and others worried they had been moved into a managed care plan. Neither is the case.

What's changing in 2027

In its CY 2027 physician fee schedule final rule, published in the Federal Register on November 9, 2026, CMS finalized a new timing rule for the ACO beneficiary notice. Beginning January 1, 2027, Shared Savings Program ACOs must furnish the standardized written notice to the beneficiaries who must receive it by May 30 of each performance year, unless CMS specifies a later date during the year.

Under the rule that was in place through 2026, the notice had to be given at or before your first primary care visit with an ACO participant during the first performance year you had such a visit. CMS acknowledges that, under the new approach, people whose first visit of the year happens before May 30 could receive the notice later than they would have under the old rule.

CMS also removed, starting January 1, 2027, the earlier requirement that ACOs follow up with a verbal or written communication within 180 days after the initial notice.

In addition to the written notice, ACO participants must post signs in their facilities and, where people get primary care, make the standardized written notice available on request.

What the notice must tell you

Whenever you receive it, the standardized notice must explain:

• That your providers participate in the Medicare Shared Savings Program;
• That you can decline to have Medicare share your claims data with those providers; and
• How to identify or change the primary care provider you are aligned with for ACO purposes.

That last point matters. "Alignment" is how Medicare decides which ACO, if any, is accountable for your care — generally based on where you get most of your primary care. You keep the right to see any Medicare provider; alignment is an internal Medicare bookkeeping concept, not a network restriction.

Your data-sharing choice

Data sharing is the piece most people have questions about. When your providers are in an ACO, Medicare can share your claims information with them — things like visits with other doctors, prescriptions filled, and tests done — so the care team has a fuller picture. Many people find this useful. Others prefer to keep that information private.

If you don't want Medicare to share your information with your ACO providers, you can call 1-800-MEDICARE to opt out. Even if you opt out, Medicare may still share general information with an ACO to help measure provider quality. Opting out does not affect your Medicare coverage, your bills, or your ability to see your doctor.

What this does not affect

The ACO notice has nothing to do with enrollment choices, premiums, or plan selection. Your decisions during the Annual Enrollment Period (October 15 – December 7, 2026, for coverage that takes effect January 1, 2027) are separate.

A few other 2027 program-level facts worth keeping in mind:

• The Part D out-of-pocket cap rises to $2,400 in 2027 (up from $2,100 in 2026).
• The most any Part D plan may charge as a deductible in 2027 is $700.
• The Part D base beneficiary premium for 2027 is $41.33 — a national figure used in the late-enrollment penalty calculation; actual plan premiums are set plan by plan.
• Social Security announced a 3.6 percent cost-of-living adjustment for benefits payable beginning January 2027.

The 2027 Part B standard premium and deductible, and the 2027 IRMAA income brackets and surcharges, are announced by CMS in the fall — typically November. Watch for the official release rather than relying on estimates.

If you have Medicaid or Extra Help

Since 2025, people with Medicaid or Extra Help have a monthly Special Enrollment Period to move to Original Medicare with a stand-alone Part D plan, or to switch stand-alone Part D plans. Full-benefit dual-eligible individuals can join an integrated D-SNP in any month.

Thinking about coverage choices

As you review options, remember that Original Medicare (often paired with a stand-alone Part D plan and, for some, a Medigap policy) and Medicare Advantage are structured differently. Original Medicare lets you see any provider that accepts Medicare and generally relies on separate drug coverage; Medigap can help with cost-sharing. Medicare Advantage plans typically use networks and often bundle drug coverage and extra benefits, with their own rules for referrals and prior authorization. Neither approach is right for everyone — the trade-offs depend on your health, your providers, and your preferences.

Where to go next

For official, current information, visit Medicare.gov or call 1-800-MEDICARE (TTY 1-877-486-2048), available 24 hours a day, seven days a week. That's also the number to use if you want to opt out of ACO claims-data sharing.

This article is educational and is published by an independent, privately owned Medicare education site. It is not affiliated with the federal government or any insurance company.