Medicare Open Enrollment 2027: The Provider Checklist for January

Medicare open enrollment 2027 runs from October 15 to December 7, 2026, and every plan change takes effect on January 1, 2027. For your patients, it’s a choice of plans. For your practice, it’s the reason January claims deny. A patient who quietly moves from Original Medicare to a Medicare Advantage plan, or from one plan to another, will show up in January with the same face and a different payer.

This guide gives you the key dates, the 2027 numbers from CMS, a January checklist and fixes for the denials that follow open enrollment.

Medicare Open Enrollment 2027: Key Dates

Sources: CMS press release (September 28, 2026) and Medicare.gov.

The 2027 Numbers From CMS

CMS released its 2027 Medicare Advantage and Part D numbers on September 28, 2026.

Source: CMS, “Medicare Advantage and Medicare Prescription Drug Programs Expected to Remain Stable in 2027.”

What this means for practices: lower premiums and thousands of plan choices make switching easy. Nearly half of your Medicare patients may be in Medicare Advantage next year, and each MA plan sets its own network, authorization and claim rules.

Why Open Enrollment Hits Your January Claims

Original Medicare and Medicare Advantage look the same to a patient, because both are “Medicare.” To your billing team they are different payers:

Patients rarely tell the front desk they switched plans. Many still carry their old Medicare card. If no one checks, the claim goes to the wrong payer, often weeks after the visit.

Our insurance eligibility verification services are built for exactly this rush.

Medicare Open Enrollment 2027 Checklist for Providers

Before January (November–December)

1. List your Medicare Advantage contracts for 2027. Note any plan you are leaving, joining or renegotiating.
2. Remind patients to bring their new card to the first visit in January. A short note at checkout or in your patient portal works.
3. Find patients with ongoing care that crosses January 1: SNF residents, home health patients, therapy series and behavioral health programs. They need a coverage check before January 1, not after.
4. Update payer IDs and plan names in your practice management system for any new 2027 plans.

In January (and through March)

5. Re-verify eligibility for every Medicare patient at the first visit of the year. Use the MAC eligibility tool or your clearinghouse to see if the patient now has an MA plan.
6. Scan the new card (front and back) and update the payer, member ID and plan type.
7. Check network status for the new plan before the visit, or tell the patient about out-of-network costs.
8. Get new prior authorizations under the new plan. An authorization from the old payer does not carry over.
9. Re-check MA patients monthly through March, because they can switch again until March 31.
10. Watch the first January remits for wrong-payer and eligibility denials, and fix the pattern fast.

Worked Example: A January SNF Admission

Example only. The facility and resident are fictional. The payment uses FY 2027 urban SNF PPS rates and the 0.9343 wage index from the CMS final rule example.

A resident had Original Medicare in 2026. During open enrollment she switched to a Medicare Advantage HMO, starting January 1, 2027. On January 5 she is admitted to an urban SNF after a hospital stay. The admission team still has her old Medicare card on file.

How the $11,490.93 is built: days 1–3 at $1,086.14 (NTA tripled) plus days 4–14 at $748.41, using the FY 2027 rates. A 30-second eligibility check on January 5 would have shown the MA plan and triggered an authorization request before admission.

January Denials and How to Fix Them

Watch timely filing too. A claim sent to the wrong payer does not stop the new payer’s filing clock. If January denials keep piling up, our denial management services can work them, and our guide on how to reduce claim denials covers prevention.

SNF, Home Health, Behavioral Health and FQHC

• Skilled nursing facilities: Original Medicare doesn’t require prior authorization for a covered SNF stay, but many MA plans do. Verify coverage before every January admission. See our guides on FY 2027 SNF Medicare daily rates and revenue code 0022.
• Home health: Periods of care often cross January 1. If a patient moves to an MA plan, the new plan’s authorization and billing rules apply to dates on and after January 1.
• Behavioral health: MA plans may use a separate behavioral health administrator with its own payer ID and authorization rules. Check who manages the behavioral health benefit, not just the plan name.
• FQHCs: MA plans pay FQHCs under their contracts, and Medicare may owe a supplemental payment. Make sure the claim goes to the right payer first.

Texas Note

Texas has many Medicare Advantage plans, and plan counts and premiums vary by county. CMS publishes a Texas page in its 2027 state-by-state fact sheets. For Texas practices, two extra checks matter in January:

• Dual-eligible patients: patients with both Medicare and Texas Medicaid may change their Medicare plan during open enrollment. Re-check the Medicaid side too, so crossover and coinsurance claims go to the right place.
• Texas Medicaid’s short filing window: Texas Medicaid claims are generally due within 95 days. A secondary claim delayed by a January wrong-payer denial can run out of time.

Need help with Texas payers? See our Austin medical billing company page.

FAQs

When is Medicare open enrollment for 2027?

Medicare open enrollment for 2027 coverage runs from October 15 to December 7, 2026. Plan changes made during this period take effect on January 1, 2027. People already in a Medicare Advantage plan get another chance to switch from January 1 to March 31, 2027.

How does Medicare open enrollment affect providers?

Patients can switch between Original Medicare and Medicare Advantage, or between MA plans, starting January 1. If the practice bills the old payer, the claim is rejected or denied. New plans may also have different networks and prior authorization rules, so January brings a spike in eligibility denials.

Should providers re-verify Medicare eligibility in January?

Yes. Re-verify every Medicare patient’s coverage at the first visit of the year, even established patients. Check whether they now have a Medicare Advantage plan, confirm network status and get any authorizations the new plan requires. Re-check MA patients through March.

What is the Medicare Advantage Open Enrollment Period?

It runs from January 1 to March 31 each year and is only for people already in a Medicare Advantage plan. They can switch to another MA plan or go back to Original Medicare. The new coverage starts on the first of the month after the plan gets the request.

What denial codes are common after open enrollment?

The most common are CO-109 (claim sent to the wrong payer), CO-27 (coverage ended), CO-31 (patient not identified as a member), CO-197 (no prior authorization) and CO-242 (out of network). Most of them can be prevented with a coverage check before the visit.

What is the average Medicare Advantage premium in 2027?

CMS projects the average Medicare Advantage monthly premium will fall from $14.37 in 2026 to $12.00 in 2027, a 16.5% decrease. CMS also projects about 34 million MA enrollees in 2027, around 47.4% of people with Medicare.

Get Ready for January Now

Medicare open enrollment 2027 is a patient decision with a provider price tag. The practices that get paid on time in January are the ones that re-verify every Medicare patient, update payers and get authorizations before the first visit of the year.

DocMBS can take January eligibility checks off your team’s plate. See our eligibility verification services, or book a free billing review to plan for January.

Sources

• CMS: Medicare Advantage and Medicare Prescription Drug Programs Expected to Remain Stable in 2027, September 28, 2026
• CMS: 2027 Medicare Advantage and Part D state-by-state fact sheets
• Medicare.gov: Joining a plan: enrollment periods
• Federal Register: FY 2027 SNF PPS Final Rule (CMS-1843-F)

Last updated: October 2026. This article is for education only. Confirm coverage, network and authorization rules with each Medicare Advantage plan before billing