Outpatient Surgery Bills: Hospital Outpatient Department vs. Ambulatory Surgical Center

Outpatient surgery can happen in a hospital outpatient department or in an ambulatory surgical center (ASC), a separate facility for same-day surgery, and in either place you usually get at least two bills: one from the facility and one from the surgeon, plus possibly anesthesia. For an ASC, Medicare.gov says you pay 20% of the Medicare-approved amount to both the center and the doctors after the Part B deductible ($283 in 2026). Medicare's Procedure Price Lookup tool can show how national average costs compare between the two settings for many procedures.

What's the difference between the two settings?

• Hospital outpatient department: Part of a hospital. You aren't admitted as an inpatient, even if you're in the hospital building for hours.
• Ambulatory surgical center: A facility that only does outpatient procedures. Medicare.gov says in most cases, ASCs release patients within 24 hours.

Your doctor decides where to do the procedure based on your health and the procedure. Some people may be able to choose.

What do I pay at an ambulatory surgical center?

Medicare.gov says that after you meet the Part B deductible, you pay 20% of the Medicare-approved amount to both the ASC and the doctors who treat you.

There's an exception for some preventive procedures. For example, Medicare.gov notes that if your doctor removes a polyp during a screening colonoscopy, you may pay 15% of the Medicare-approved amount.

What do I pay at a hospital outpatient department?

Medicare.gov says you usually pay the hospital a copayment for each service you get in a hospital outpatient department, plus usually 20% of the Medicare-approved amount for your doctors' services, after the Part B deductible. In most cases, the hospital copayment for a service can't be more than the Part A deductible. It may be higher at a critical access hospital.

Why can the same surgery cost different amounts?

The Medicare-approved amount for the same procedure can differ between the two settings, so what you owe can differ too. Medicare's Procedure Price Lookup tool (below) shows both amounts.

How do I compare costs before surgery?

Use Medicare's Procedure Price Lookup tool. Medicare.gov says it compares national average costs for procedures in ambulatory surgical centers and hospital outpatient departments. It shows the total Medicare-approved amount and what a person with Original Medicare might pay without other coverage.

Keep in mind:

• The tool shows national averages. Your costs can differ by location.
• It doesn't include every doctor's fee or extra test.
• Your Medigap or Medicare Advantage plan changes what you pay.

Then ask your surgeon's office:

• "Where will this be done, and why?"
• "Is there an ASC option for this procedure?"
• "Who will bill me: the facility, the surgeon, anesthesia, a lab?"
• "Do all of them accept Medicare assignment?"

Why did I get several bills for one surgery?

It's normal to get:

• A facility bill from the hospital or ASC.
• A surgeon's bill.
• An anesthesia bill.
• A pathology or lab bill, if tissue was tested.

Each should appear on your Medicare Summary Notice (MSN) as a separate claim.

How do I check outpatient surgery bills?

1. Match each bill to your MSN or your plan's Explanation of Benefits (EOB).
2. Compare what you owe with the "maximum you may be billed."
3. Check the setting. If the bill lists hospital outpatient charges but you had surgery at an ASC, ask why.
4. Watch for preventive procedures. For a screening colonoscopy, the cost sharing rules differ.
5. Confirm Medigap paid.
6. Ask for itemized bills if anything is unclear.

What about Medicare Advantage?

Medicare Advantage plans set their own copays for outpatient surgery and may charge different amounts for ASCs and hospital outpatient departments. Some require prior authorization. Check your plan's Evidence of Coverage, and ask the plan which facilities are in network.

What if I can't afford my share?

Ask the facility about financial assistance before you pay. Nonprofit hospitals must have a written financial assistance policy. If you qualify for the Qualified Medicare Beneficiary (QMB) program, providers can't bill you for Medicare cost sharing on covered services. You can also ask for an interest-free payment plan once you know the bill is correct.

What should I say when I call the billing office?

"I had outpatient surgery on [date] at [facility]. My Medicare Summary Notice shows a maximum I may be billed of $[amount], but your bill is $[amount]. Can you explain the difference? Also, please confirm my supplemental insurance was billed."

Frequently asked questions

Is outpatient surgery cheaper at an ambulatory surgical center?

It can be. Use Medicare's Procedure Price Lookup tool to compare national averages for your procedure.

What do I pay at an ASC with Original Medicare?

Medicare.gov says you pay 20% of the Medicare-approved amount to both the ASC and your doctors after the Part B deductible.

Why did I get separate bills from the surgeon and the facility?

Facilities and doctors bill separately for outpatient surgery. Anesthesia and lab services may bill separately too.

Can I choose where my surgery is done?

Sometimes. Ask your doctor whether an ASC is an option and why they recommend one setting.

Got a stack of surgery bills?

Bill Review Coach is a monthly medical bill review service for seniors and their families. Snap photos of your surgery bills and Medicare notices, and we'll match them up, flag what doesn't fit, and tell you what to say when you call. You make the calls and write the emails; we help you know what to say.