Medicare takes money from your paycheck and uses it to pay doctors, hospitals, and other providers

Medicare is a federal health insurance program for people 65 and older, some younger people with disabilities, and people with end-stage renal disease. The program is funded through payroll taxes — money taken directly from your wages while you work, and matched by your employer. Once you turn 65 or become may be able to access, Medicare uses that pool of money to pay hospitals, doctors, and other medical providers when you receive care.

The payment flow is straightforward: you go to a doctor or hospital that accepts Medicare, they bill Medicare directly, and Medicare pays them a set amount based on the service provided. You typically pay a portion yourself through deductibles and copayments, but Medicare covers the rest. Understanding how this system works helps you know what to expect when you receive a bill and why the amount Medicare pays may differ from what the provider initially charged.

Key Takeaways

  • Medicare is funded by payroll taxes (2.9% of your wages split between you and your employer) and general tax revenue, not by a separate insurance premium you pay upfront.
  • When you receive care, the provider bills Medicare directly, and Medicare pays them according to a fee schedule that varies by service and location.
  • You receive an Explanation of Benefits (EOB) after each claim, which shows what Medicare paid, what you owe, and what the provider cannot bill you for.
  • Medicare Part A (hospital insurance) and Part B (medical insurance) have different deductibles and payment structures, so your out-of-pocket costs depend on which part covers your care.

The two main funding sources: payroll taxes and general revenue

While you work, you and your employer each pay 1.45% of your wages into Medicare Part A (hospital insurance). This is separate from Social Security tax and appears on your pay stub as "Medicare tax." If you earn over a certain threshold ($200,000 for single filers, $250,000 for married couples filing jointly), you pay an additional 0.9% on income above that amount.

Part B (medical insurance for doctor visits and outpatient care) and Part D (prescription drug coverage) are funded differently. Part B is funded partly by general federal tax revenue and partly by premiums you pay monthly once you enroll. Part D premiums vary by plan and are paid directly to the insurance company offering the plan. The exact breakdown of how much comes from taxes versus premiums changes annually, but the key point is that Medicare is not a savings account where your payroll taxes sit waiting for you — it is a pay-as-you-go system where current workers' taxes pay for current beneficiaries' care.

How providers bill Medicare and what happens next

When you see a doctor or go to a hospital, the provider submits a claim to Medicare electronically or by mail. The claim includes the diagnosis code, the procedure or service code, and the amount the provider is charging. Medicare then checks whether the service is covered under your plan, whether you have met your deductible, and what the provider is allowed to charge for that service in your geographic area.

Medicare pays the provider based on its fee schedule — a list of approved amounts for thousands of medical services. The fee schedule varies by location because the cost of living and operating a medical practice differs across the country. For example, a doctor visit in New York City may have a higher approved amount than the same visit in a rural area. The provider cannot bill you for the difference between what they charged and what Medicare approved, with rare exceptions for services Medicare does not cover.

The entire process typically takes two to four weeks. During that time, you will not hear anything unless there is a problem with the claim — such as missing information or a service that requires prior authorization. Once Medicare processes the claim, both you and the provider receive notice of the decision.

Understanding your Explanation of Benefits (EOB)

After Medicare pays a claim, you will receive an Explanation of Benefits (EOB) in the mail. This document shows what the provider charged, what Medicare approved, what Medicare paid, and what you owe. The EOB is not a bill — it is a summary of what happened with your claim. Your actual bill comes separately from the provider.

The EOB breaks down the payment like this: the provider's charge, the Medicare-approved amount (which may be lower), the amount Medicare paid (usually 80% of the approved amount for Part B services after you meet your deductible), and your responsibility. If the provider charged $200 but Medicare's approved amount is $150, Medicare will not pay on the $50 difference, and the provider cannot bill you for it — that difference is written off.

Read your EOB carefully, especially if you received care from an out-of-network provider or if a service was denied. If you disagree with what Medicare paid or did not pay, you have the right to appeal. The EOB includes instructions for filing an appeal, and you typically have 120 days from the date on the notice to start the process.

Part A versus Part B: different deductibles and payment structures

Part A covers inpatient hospital stays, skilled nursing facility care, hospice, and home health services. Part A has a deductible that applies per benefit period (not per year). For 2024, the Part A deductible is $1,632 per benefit period. A benefit period begins the day you enter the hospital and ends 60 days after you leave without receiving any inpatient care. If you are readmitted within 60 days, you are still in the same benefit period and do not pay another deductible.

Part B covers doctor visits, outpatient care, lab tests, and durable medical equipment. Part B has a separate annual deductible (currently $240 per year) and a coinsurance amount. After you meet your deductible, Medicare typically pays 80% of the approved amount, and you pay 20%. The deductible resets every January 1st.

Because the deductibles and payment structures are different, your out-of-pocket costs depend on which part covers your care. A hospital stay uses Part A, so you pay the Part A deductible. A doctor visit uses Part B, so you pay the Part B deductible and then 20% coinsurance. If you have supplemental insurance (Medigap) or a Medicare Advantage plan, those plans may cover some or all of your deductible and coinsurance.

What happens when a provider is out-of-network

Medicare does not have a network in the traditional sense — most providers accept Medicare nationwide. However, some providers choose not to accept Medicare at all, and a few accept Medicare but do not accept assignment, meaning they do not agree to accept Medicare's approved amount as payment in full.

If you see a provider who does not accept Medicare, you will likely pay the full bill upfront and then submit a claim to Medicare yourself. Medicare will pay you based on its approved amount, but you may owe the provider the difference between what they charged and what Medicare paid. This is called balance billing, and it can be expensive.

If a provider accepts Medicare but does not accept assignment, they can bill you for up to 15% more than Medicare's approved amount. This is called limiting charge billing. For example, if Medicare approves $100 for a service, a non-participating provider can charge you up to $115. You should always ask a provider before your visit whether they accept Medicare assignment to avoid surprises.

Medicare Advantage and how payments work differently

If you choose a Medicare Advantage plan (Part C) instead of Original Medicare, the payment structure changes. Medicare Advantage plans are offered by private insurance companies and include all Part A and Part B coverage plus usually Part D (prescription drugs). Instead of Medicare paying providers directly, Medicare pays the insurance company a fixed monthly amount per member, and the insurance company then pays providers.

With Medicare Advantage, you typically have a network of providers, similar to a traditional health insurance plan. You may pay a copayment for each visit instead of a deductible and coinsurance. The insurance company negotiates rates with providers, so the amount they pay may differ from what Original Medicare would pay. Your out-of-pocket costs depend on the specific plan you choose.

The key difference for payment purposes is that you deal with the insurance company, not Medicare directly. If you have a question about a claim or payment, you contact the insurance company's customer service, not Medicare.

Frequently Asked Questions

Why did Medicare pay less than the provider charged?

Medicare has an approved amount for each service based on location and service type. If the provider charged more than the approved amount, Medicare only pays on the approved amount. The provider cannot bill you for the difference — that is written off. You can see the approved amount on your EOB.

Can I see how much Medicare approved for my service before I go to the doctor?

Yes. You can search the Medicare Physician Fee Schedule on the Centers for Medicare & Medicaid Services (CMS) website, or call your doctor's office and ask what Medicare approves for the specific service you need. Knowing this in advance helps you understand what you will owe.

What if I think Medicare paid the wrong amount?

You have the right to appeal any Medicare decision. Your EOB includes instructions for filing an appeal. You typically have 120 days from the date on the notice to request a review. You can appeal on your own or ask your doctor's office to help.

Do I have to pay Medicare back if I receive a refund from my provider?

No. If a provider refunds you money because they overcharged or made an error, that refund is yours to keep. Medicare does not ask for money back in that situation. However, if Medicare overpaid due to an error on the claim, Medicare may ask the provider to return the overpayment, but this does not affect you directly.

How long does it take Medicare to pay a claim?

Most claims are processed within two to four weeks. Complex claims or claims that require additional review may take longer. You can check the status of a claim by logging into your Medicare account on Medicare.gov or by calling Medicare at 1-800-MEDICARE.