Medicare Supplement Birthday Rule: Every State With One for 2027

Each row lists the window, which plans you can move to and which insurers you can pick. Windows are counted from your birthday unless noted. Equal or lesser means a plan with the same or fewer benefits, such as Plan G to Plan N.

Our compilation from the NAIC birthday rule chart (May 11, 2026), the Delaware Department of Insurance SB 71 fact sheet, New Mexico’s SB 21 summary and state insurance guidance. Rules change often; confirm with your state insurance department before switching.

Missouri works on the same idea but uses your policy’s anniversary date instead of your birthday. Under the state’s Medigap regulation, if you end your policy within 30 days of its anniversary, you can buy the same plan from any insurer that sells it in Missouri. A renewal notice or bill that shows your anniversary date is the usual proof.

In Connecticut, Massachusetts, Maine and New York, broader guaranteed issue rules mean a birthday window matters less, because at least some Medigap coverage is available without underwriting all year. See our Missouri Medicare Supplement guide for local plan options.

Birthday rules have spread quickly. Many guides online still list fewer than ten states. These are the rules that started most recently.

Start dates from state laws and insurance department notices as summarized by the NAIC and state agencies.

A same-insurer rule is still useful. Large carriers often sell several policy forms with different rate histories, and an affiliate may price the same letter lower. A same-letter rule works best when your current company’s premium has drifted well above competitors’ prices for that letter.

If you are leaving Medicare Advantage, look instead at federal guaranteed issue rights and your trial right. For switches outside any window, our guide to switching Medigap plans without underwriting covers the other options.

Insurers argue that letting people switch without underwriting can make premiums higher for all policyholders, and KFF Health News reported in April 2026 that Medigap rate increases above 10% have become common. Some new laws respond to that concern directly. West Virginia’s requires the insurance commissioner to report on premium trends each year, and Delaware’s bars insurers from rating up birthday-rule switchers.