Leaving the Marketplace When SSDI Medicare Starts

Marketplace coverage does not end automatically when Medicare begins after an SSDI award, and leaving it running can mean repaying tax credits and paying two premiums at once. HealthCare.gov's page on changing from the Marketplace to Medicare instructs people starting Medicare to update their Marketplace application so the plan ends the day before Medicare takes effect.

The transition is a task with a deadline, not a single phone call. You need to know your Medicare start month, end the Marketplace plan with the right effective date, keep the plan for any family members who still need it, and resist the urge to decline Part B along the way. Done in order, the switch is smooth. Done out of order, it can cost money every month for years.

Why a Marketplace Plan Stops Working Once Medicare Starts

Medicare is not part of the Health Insurance Marketplace, and the two systems do not coordinate benefits. According to HealthCare.gov, once you have Medicare Part A (Hospital Insurance) or Part C (Medicare Advantage), you no longer qualify for any Marketplace savings, including premium tax credits and cost-sharing reductions. A Marketplace plan also does not pay your Medicare deductibles or coinsurance, and it is never a substitute for Part B (Medical Insurance).

The law draws a hard line between the programs. HealthCare.gov states that it is against the law for someone who knows you have Medicare to sell you a Marketplace plan, and that rule applies even if you have only Part A or only Part B. The Marketplace does not sell Medigap supplements or Medicare drug plans either, so the coverage you will rely on after Medicare starts has to come from Medicare itself.

The Month SSDI Turns Into Medicare

Most SSDI beneficiaries become entitled to Medicare on the first day of the 25th month of disability cash benefit entitlement, a timeline set by Section 226 of the Social Security Act and 42 CFR 406.12. Because the five-month waiting period under 20 CFR 404.315 must be served first, Medicare usually starts about 29 months after your established disability onset date. People diagnosed with ALS skip the 24-month wait entirely under the ALS Disability Insurance Access Act of 2020.

The Social Security Administration enrolls you in Part A and Part B automatically and mails your Medicare card a few months before coverage begins. That automatic Part B enrollment protects you. Declining it just to keep a Marketplace plan is one of the costliest mistakes a transitioning beneficiary can make.

Ending the Marketplace Plan Correctly, Step by Step

1. Confirm your exact Medicare start date. Your Notice of Award letter or your personal my Social Security account shows the month entitlement begins. Medicare coverage starts on the first day of that month.
2. Report the Medicare start date in your Marketplace application up to 3 months before it takes effect. HealthCare.gov gives the example of Medicare beginning May 1: you can update your application as early as February 1, and your Marketplace coverage then ends April 30, the day before Medicare starts.
3. End only your own coverage. If a spouse or child is on the same Marketplace plan, update the application carefully and confirm their coverage continues, as HealthCare.gov advises.
4. Keep paying your Marketplace premium through the final month of coverage. A missed final payment can create a gap right at the moment your medical care is switching systems.
5. Do not cancel before Medicare actually starts. If your Medicare start date shifts for any reason, you want continuous coverage, and an early cancellation can leave weeks uninsured.

The Tax Credit Repayment Trap

Most subsidized Marketplace enrollees receive an advance premium tax credit each month, applied directly to the premium. HealthCare.gov explains that eligibility for those savings ends once you have Part A or Part C. Any advance credits paid for months after your Medicare entitlement are credits you were not eligible to receive.

Those credits are reconciled on your federal income tax return, which usually means repaying them at tax time. A beneficiary who keeps a subsidized plan for a full extra year after Medicare starts can face a repayment running into the thousands of dollars. Ending the plan through your Marketplace application, on the schedule described above, prevents the problem cleanly.

Do Not Delay Part B Because of the Marketplace Plan

A Marketplace plan you bought yourself is not job-based coverage, and it gives you no special enrollment period for Part B. HealthCare.gov describes an 8-month special enrollment period for Part B only for people covered through an employer group plan or a SHOP Marketplace plan based on current employment, yours or a spouse's.

If you skip Part B without that protection, Medicare.gov's guidance on avoiding late enrollment penalties explains the cost: the penalty is 10 percent of the Part B premium for each full 12-month period you could have enrolled but did not, and it stays on your premium for as long as you have Part B. With the 2026 standard premium at $202.90 per month, according to CMS's 2026 Medicare costs fact sheet, a two-year delay adds 20 percent to the premium every month, permanently.

People who do miss the deadline sign up during the General Enrollment Period, which runs January 1 to March 31 each year, with coverage starting the month after enrollment. Waiting for that window means months of uncovered doctor and outpatient care, plus the penalty.

What Coverage Replaces the Plan

Once Medicare starts you choose between Original Medicare plus a Part D drug plan, or a Medicare Advantage plan that usually bundles drug coverage. Either way, the 2026 Part B deductible is $283 per year under the CMS fact sheet, and Medigap supplements to fill that gap are a state-by-state question for people under 65, since Medicare.gov notes that federal law does not guarantee Medigap availability to beneficiaries under 65.

Two timing rules matter in your first year. Medicare's annual Open Enrollment Period runs October 15 to December 7, the window for switching Medicare Advantage and drug plans. And if you delayed Part D because your Marketplace plan covered prescriptions, check its creditable coverage notice carefully. HealthCare.gov warns that prescription coverage in a Marketplace plan does not have to match the value of Part D, and plans must tell you in writing each year whether their drug coverage is creditable. Going without creditable drug coverage after Medicare starts triggers a Part D late enrollment penalty that, like the Part B penalty, follows you permanently.

Frequently Asked Questions

When should I cancel my Marketplace plan after Medicare starts? Set your Marketplace coverage to end the day before your Medicare begins. HealthCare.gov lets you report your Medicare start date up to 3 months in advance so the two coverages never overlap.

Do I have to repay premium tax credits I received after Medicare started? Yes. Once you have Medicare Part A or Part C you do not qualify for Marketplace savings, and credits paid for those months are reconciled on your federal tax return, which usually means repaying them.

Can I keep my Marketplace plan instead of signing up for Medicare? Generally no. HealthCare.gov explains that it is against the law for someone who knows you have Medicare to sell you a Marketplace plan, with narrow exceptions such as people who pay a premium for Part A.

This article is general information about benefits and health coverage, not legal advice. Program rules, premiums, and penalties change over time, and every situation is different. Consult a qualified representative or contact the Social Security Administration and Medicare directly for guidance on your specific case.