Illinois has a Medicare Supplement (Medigap) "birthday rule," but it is narrower than the one you may have read about in other states. In Illinois, only policyholders between 65 and 75 get a 45-day window each year, starting on their birthday, to switch to an equal-or-lesser plan from the same insurer with no medical underwriting. This guide explains exactly how the Illinois birthday rule works, who qualifies, how the standardized A-through-N plans fit together, which plans are closed to newer enrollees, and who regulates Medigap in the state.
How Medigap works in Illinois
A Medigap policy is private insurance that pays the deductibles and coinsurance Original Medicare leaves to you. Medigap (Medicare Supplement Insurance) works only alongside Original Medicare, not with a Medicare Advantage plan, and each policy covers one person. A married couple who both want coverage need two policies.
Illinois uses the federal standardized framework. Medigap is sold as lettered plans, A through N, and the benefits inside each letter are fixed by federal rule. A Plan G from one Illinois insurer covers exactly what a Plan G from another covers. Insurers compete on price, service, and rate stability, not on what the plan pays. That makes the plan letter your first decision and the insurer your second.
The gaps Medigap closes are real. After the Part B deductible ($283 in 2026), Original Medicare pays 80% of the approved amount for most outpatient care and leaves you the other 20%, with no annual cap. Part A adds a hospital deductible of $1,736 per benefit period in 2026, and that deductible can apply more than once in a year. Medigap caps that exposure.
The Illinois birthday rule
Illinois gives Medigap policyholders an annual birthday rule, but its terms are specific. Under Illinois law, a Medigap policyholder who is at least 65 but no more than 75 years old is entitled to a 45-day open enrollment period each year, beginning on their birthday, during which they may switch without medical underwriting to a Medigap policy of equal or lesser benefits offered by the same insurer, according to the Illinois Department of Insurance.
Compared with broader birthday rules in other states, Illinois adds two real limits. First, it is capped at ages 65 through 75, so a 78-year-old policyholder cannot use it. Second, the switch must stay with your current insurer; the Illinois rule does not let you move to a different company without underwriting. Within those bounds, it is still a useful protection: if your insurer sells a less expensive equal-or-lesser plan, you can move into it once a year without proving you're healthy.
The "equal or lesser benefits" limit is the key constraint. You can move sideways (Plan G to another Plan G the insurer offers) or down to a less generous letter (Plan G to Plan N), but the birthday rule does not let you move up to a more comprehensive plan. Moving up still requires medical underwriting outside a guaranteed-issue window.
How to use the Illinois birthday rule
The window is short and the terms are narrow, so plan ahead.
- Confirm you qualify. You must be a current Medigap policyholder between ages 65 and 75. If you are older than 75, the birthday rule no longer applies to you.
- Know your date. The 45-day window begins on your birthday. Ask your insurer in advance what equal-or-lesser plans it offers so you can act as soon as the window opens.
- Stay with your insurer, go equal or lesser. Identify your current plan letter, then pick a same-insurer policy of the same letter or a less comprehensive one. A Plan G holder can switch to another Plan G or down to Plan N from the same company.
- Apply during the window. Submit the application within the 45 days and tell the insurer you are using Illinois's birthday rule. The insurer cannot apply medical underwriting to the switch.
- Keep the old policy until the new one starts. Don't cancel existing coverage until the new policy is confirmed and in force, so you're never uninsured.
Because the benefits inside a letter are standardized, a same-letter switch changes your premium, not your coverage. If you move to a lesser letter, your cost-sharing changes to match that letter.
Plan G and Plan N: the common choices
For someone newly eligible for Medicare, the practical choice in Illinois narrows to two plans.
Plan G is the most complete plan still available to people who became eligible on or after January 1, 2020. It covers every gap in Original Medicare except the annual Part B deductible: the Part A hospital deductible, Part A and Part B coinsurance, skilled nursing facility coinsurance, and Part B excess charges. After you pay that one Part B deductible for the year, a Plan G holder generally has no further cost-sharing on Medicare-covered services.
Plan N covers the same major gaps but shifts a little cost back to you. It pays the Part B coinsurance except for a copay of up to $20 for some office visits and up to $50 for emergency-room visits that don't lead to an inpatient admission, and it does not cover Part B excess charges. In exchange, Plan N premiums are usually lower than Plan G premiums.
| Feature | Plan G | Plan N |
|---|---|---|
| Part A hospital deductible | Covered | Covered |
| Part B coinsurance | Covered in full | Covered, minus up to $20 office / $50 ER copays |
| Part B excess charges | Covered | Not covered |
| Annual Part B deductible ($283 in 2026) | You pay it | You pay it |
| Skilled nursing facility coinsurance | Covered | Covered |
| Relative premium | Higher | Lower than Plan G |
Plans C and F are closed to newer enrollees
Plans C and F once covered the annual Part B deductible on top of the other gaps, which made Plan F the most complete plan on the market. Under the Medicare Access and CHIP Reauthorization Act of 2015 (MACRA), any Medigap plan that pays the Part B deductible is closed to people who first became eligible for Medicare on or after January 1, 2020.
The closure works by eligibility date, not purchase date. If you became eligible for Medicare before January 1, 2020, you can still buy or keep Plan C or Plan F in Illinois. If you became eligible on or after that date, those two plans are off the table, which is why Plan G has become the default top-tier choice for newer enrollees: it's identical to Plan F except that you pay the one Part B deductible yourself.
When you can buy or switch in Illinois
Illinois gives you more than one protected window. Three matter most.
- The federal Medigap Open Enrollment Period. This is a one-time, six-month window that begins the first month you're both age 65 or older and enrolled in Medicare Part B. During it, insurers must sell you any Medigap policy they offer at their best available rate regardless of your health, with no medical underwriting. This is the single best time to buy, because you can choose any plan, including Plan G.
- The annual birthday rule. The 45-day window described above, repeating each year for policyholders ages 65 to 75, for switching to an equal-or-lesser plan from the same insurer with no underwriting.
- Federal guaranteed-issue rights. Certain life events, such as losing other coverage or an insurer leaving the market, trigger a federal guaranteed-issue right to buy specific plans without underwriting.
Outside these windows, an Illinois insurer can require medical underwriting and charge more, or decline to sell you a policy, based on your health. That's why the choice between Plan G and Plan N is best made during your six-month open enrollment: the birthday rule won't cover a move up to a richer plan, and it ends at age 75, so underwriting could later make an upgrade expensive or impossible.
What Medigap costs and how it's priced in Illinois
Medigap premiums vary widely. The benefits inside a letter are fixed, but the price is not: it depends on the insurer, your age, and in many cases your gender and tobacco use. Nationally, median Plan G premiums run about $150 to $175 a month and Plan N about $125 to $150, though your Illinois quote can fall outside those ranges.
Insurers use one of three pricing methods, which shapes how your premium changes as you age:
- Community-rated policies charge everyone the same premium regardless of age.
- Issue-age-rated policies base your premium on your age when you buy, and that starting point doesn't rise simply because you get older.
- Attained-age-rated policies start lower but increase as you age, so a low first-year quote can climb over time.
Ask which method each insurer uses, not just the first-year premium. The Illinois birthday rule pairs only partially with this: it lets you move to a cheaper equal-or-lesser plan from the same insurer between 65 and 75, but it will not move you to a different carrier or keep working after 75. Note that Medigap does not include prescription drug coverage, so you add a separate Part D plan for that.
Who regulates Medigap in Illinois
Illinois Medigap policies are regulated by the Illinois Department of Insurance, which oversees the insurers that sell these policies and handles consumer complaints. If you have a question or a complaint about a specific policy, that is the agency to contact.
Frequently asked questions
Illinois gives Medigap policyholders ages 65 to 75 a 45-day window each year, starting on their birthday, to switch to a Medigap policy of equal or lesser benefits from the same insurer, with no medical underwriting, per the Illinois Department of Insurance. The right ends after age 75 and does not allow switching to a different company.
No. The Illinois birthday rule only protects a switch to an equal-or-lesser plan offered by your current insurer. Moving to a different company is not covered and would require medical underwriting outside a guaranteed-issue window.
No. The birthday rule only lets you switch to a plan with equal or lesser benefits. Moving up to a more comprehensive plan, such as Plan N to Plan G, is not covered and would require underwriting. To get Plan G without underwriting, choose it during your six-month open enrollment.
Only if you first became eligible for Medicare before January 1, 2020. Plans C and F, which cover the Part B deductible, are closed to anyone who became eligible on or after that date under MACRA. Plan G is the closest available alternative; it's identical to Plan F except that you pay the annual Part B deductible yourself.
Illinois Medigap policies are regulated by the Illinois Department of Insurance, which oversees the insurers that sell these policies and handles consumer complaints.
Learn More
- Medicare plans and coverage in Illinois
- Medigap (Medicare Supplement): how the lettered plans work
- What is Medicare? Parts A, B, C, and D explained
- Original Medicare vs. Medicare Advantage
Find personalized help comparing Medicare Supplement plans in Illinois 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.