New Mexico Medigap Birthday Rule: What SB 21 Changes in 2027

The New Mexico Medigap birthday rule, created by Senate Bill 21, takes effect on January 1, 2027, so it does not yet apply to a Medigap switch made in 2026. From 2027, SB 21 requires every insurer in New Mexico's Medicare supplement (Medigap) market to give each eligible policyholder an annual window, opening on the first day of the policyholder's birthday month and lasting at least 60 days, to buy a Medigap policy offered in New Mexico of equal or lesser value without the insurer denying, delaying or pricing the policy based on the policyholder's health. Until SB 21 takes effect on January 1, 2027, a New Mexico Medigap policyholder who switches outside a federal protection can be medically underwritten.1,2

In This Guide

• How the New Mexico Medigap Birthday Rule Works
• Who Qualifies Under SB 21
• What You Can and Cannot Do During the Window
• Before 2027: Your Medigap Options Today
• The Notice Your Insurer Must Send
• Medigap vs. Medicare Advantage in New Mexico
• How to Use Your New Mexico Medigap Birthday Window
• Frequently Asked Questions
• Learn More

How the New Mexico Medigap Birthday Rule Works

Governor Michelle Lujan Grisham signed Senate Bill 21 of the 2026 session into law, amending New Mexico's Medicare Supplement Act to create an annual Medigap open enrollment period. The New Mexico Aging and Long-Term Services Department (ALTSD) said in its signing announcement that, before this law, Medicare beneficiaries in New Mexico received only a limited one-time opportunity to enroll in or change Medicare supplement plans without medical underwriting.1

SB 21's core duty is short. The enacted text says: "Every issuer participating in the market for medicare supplement policies shall offer an annual open enrollment period to all eligible policyholders." Each eligible policyholder's New Mexico Medigap open enrollment period starts on the first day of the policyholder's birthday month and, in the statute's words, remains "open for at least sixty days thereafter."1

During that window, SB 21 gives the eligible policyholder a purchase right and puts two duties on the insurer:

• The purchase right. An eligible New Mexico policyholder may buy any Medicare supplement policy offered in New Mexico of an equal or lesser value to the policyholder's current Medicare supplement policy.
• Guaranteed issue. Under SB 21, the insurer must guarantee the issuance of any Medicare supplement policy offered in New Mexico.
• No health-based treatment. Under SB 21, the insurer may not deny, delay or condition the issuance or effectiveness of the Medigap policy, or discriminate in its price, based on the policyholder's health status, claims, experience, receipt of health care or medical condition.1

The table below keeps the two periods apart, because the protections a New Mexico Medigap policyholder has in 2026 are not the ones SB 21 adds in 2027.1,2

Who Qualifies Under SB 21

SB 21 defines an "eligible policyholder" as a beneficiary of Medicare coverage under Part A or Part B of Title 18 of the federal Social Security Act "who is sixty-five years of age or older and insured under a medicare supplement policy."1

Read as a checklist, a person qualifies for New Mexico's Medigap birthday window from 2027 only if all three are true:

• The person has Medicare Part A or Medicare Part B.
• The person is 65 or older.
• The person is already insured under a Medicare supplement (Medigap) policy.1

Because the SB 21 definition names age 65 or older, a New Mexico Medicare beneficiary under 65 falls outside the statutory definition of an eligible policyholder. Someone not currently insured under a Medigap policy also falls outside it, since the definition requires being insured under one; that person's protected window is the federal Medigap Open Enrollment Period described in the section on options today.1

What You Can and Cannot Do During the Window

SB 21 describes the purchase right only for a Medicare supplement policy "of an equal or lesser value to the eligible policyholder's current medicare supplement policy offered in this state." The definitions and window provisions quoted in this guide do not spell out how that value is measured: whether by benefits, by premium, or by plan letter. Until the superintendent of insurance or your insurer explains how "equal or lesser value" will be applied, don't assume any one reading. Ask in writing before you apply.1

What the text does make plain:

• The purchase right points down or sideways. SB 21 describes the right to buy a policy of equal or lesser value; it describes no right to move to a policy of greater value.
• Preexisting conditions carry over. Under SB 21, a Medigap policy obtained through the New Mexico birthday window "shall not have any coverage exclusions related to preexisting conditions that would have been covered under the eligible policyholder's previous medicare supplement policy."1

For how Medigap preexisting-condition waiting periods work outside this window, see Brevy's guide to Medigap and preexisting conditions. For what the plan letters cover, see Medigap Plan G vs. Plan N.

Before 2027: Your Medigap Options Today

Until SB 21 takes effect, a New Mexico Medicare beneficiary shopping for Medigap relies on the federal protections below. Under federal law, you get a one-time, 6-month Medigap Open Enrollment Period that starts the first month you have Medicare Part B and are 65 or older. During the federal Medigap Open Enrollment Period, Medicare.gov says, an insurance company can't refuse to sell you any Medigap policy it offers, can't use medical underwriting to decide whether to accept your application, and can't charge you more because of pre-existing health problems. The same protection is written into Section 1882 of the Social Security Act at §1882(s)(2)(A).2

The federal Medigap Open Enrollment Period "doesn't repeat every year," in Medicare.gov's words. Outside the federal Medigap Open Enrollment Period, a Medigap insurance company is allowed to deny you a policy if you don't meet its medical underwriting requirements, you may pay more, and fewer policies may be available to you. Medicare.gov adds that you may have additional rights under state law, and New Mexico's SB 21 birthday window, described above, is one such right once it takes effect.2,1

If you want to switch Medigap policies in New Mexico before 2027, Medicare.gov's switching guidance sets out three federal points:

• Switching is limited. In most cases, Medicare.gov says, you won't be able to switch your Medigap policy outside your 6-month Medigap Open Enrollment Period except in specific situations when you have a guaranteed issue right, and you may have to pay more and answer medical questions. Brevy's guide to Medigap guaranteed issue rights covers those situations.
• Replacement credit for similar benefits. Under Social Security Act §1882(s)(2)(C), if a Medigap policy replaces one that has been in effect for 6 months or longer, the new policy may not apply any preexisting-condition, waiting, elimination or probationary period for similar benefits.
• Don't drop coverage first. Medicare.gov warns that if you drop your Medigap policy, you might not be able to get it or any policy back later.3

The Notice Your Insurer Must Send

SB 21 requires the insurer that issued an eligible New Mexico policyholder's current Medigap policy to send a notice at least 30 days, and not more than 60 days, before the policyholder's birthday window begins. Under SB 21, the notice must state:

1. the dates on which the open enrollment period begins and ends;
2. the rights SB 21 gives the eligible policyholder; and
3. any modifications to the Medigap policy the person currently holds, or any adjustments to its premiums.1

Under SB 21, the form and content of that notice must be filed with and approved by New Mexico's superintendent of insurance before insurers send it to policyholders. Once SB 21 is in effect, this notice is the document that tells a New Mexico policyholder the exact dates of the policyholder's own window, so keep it with your policy papers.1

Medigap vs. Medicare Advantage in New Mexico

Medigap helps pay your share of out-of-pocket costs in Original Medicare, not in Medicare Advantage. Medicare's booklet on Medicare Advantage states that if you're in a Medicare Advantage plan, it's illegal for anyone to sell you a Medigap policy unless you're switching back to Original Medicare, and that you can't use Medigap to pay a Medicare Advantage plan's copayments, coinsurance, deductibles or premiums. If someone tries to sell you a Medigap policy while you aren't planning to drop your Medicare Advantage plan, Medicare says to report it to your State Insurance Department.4

Two federal rules matter for a New Mexico reader weighing a move:

• Dropping Medigap for Medicare Advantage. In most cases, Medicare says, if you drop your Medigap policy to join a Medicare Advantage plan, you may not be able to get the same policy back.
• The trial right. If you join a Medicare Advantage plan for the first time and aren't happy with it, federal law gives you a "trial right" to buy a Medigap policy and a separate Medicare drug plan if you return to Original Medicare within 12 months of joining.4

SB 21's definition of an eligible policyholder requires being insured under a Medicare supplement policy, so a New Mexico beneficiary enrolled only in Medicare Advantage does not meet that definition as written.1 For the full comparison, see Original Medicare vs. Medicare Advantage and Brevy's guide to Medicare Advantage trial rights.

How to Use Your New Mexico Medigap Birthday Window

Once SB 21 is in effect, these steps help a New Mexico Medigap policyholder use the annual window.1

These steps rest on SB 21's notice and window provisions and on the federal switching protections in Section 1882.1,3

For free help with a Medigap or Medicare question, call 1-800-MEDICARE (1-800-633-4227; TTY 1-877-486-2048). Medicare.gov says you can talk or live chat with a real person 24 hours a day, 7 days a week, except some federal holidays.5

Learn More

Find personalized help comparing Medigap options in New Mexico with Brevy's care navigator at brevy.com.

The information on Brevy.com is for educational purposes only and is not a substitute for professional legal, financial, or medical advice. Rules vary by state and program and change frequently. Always verify with the relevant agency or a qualified professional. Brevy is not a law firm, financial advisor, or healthcare provider.