Medicare Part B Excess Charges in Washington: What Doctors Can Bill and Who Pays

A doctor who doesn't take Medicare assignment can bill you up to 15% more than Medicare's approved amount for that doctor. Because Medicare already approves 5% less for those doctors, the cap works out to 9.25% above what a participating doctor would get for the same service. That gap is the Part B "excess charge," and in Washington, the only standardized Medigap letters that pay it are F and G.

Medicare says most doctors, providers and suppliers accept assignment, so excess charges aren't common. But "most" isn't "all," and the bill lands on you, not on Medicare. It's worth ten minutes to understand the three kinds of providers, the math behind the cap, and what to do when a bill looks wrong.

Source: 42 CFR 414.20(b); 42 CFR 414.48(b); CMS, 2026 Medicare Parts A & B premiums and deductibles fact sheet. The 9.25% is 1.15 × 0.95.

Three kinds of providers

Under Original Medicare, every doctor or practitioner you see falls into one of three groups. Which group decides what they can bill you.

Participating providers have agreed to accept assignment on everything. Assignment means accepting the Medicare-approved amount as payment in full. They can charge you only the Part B deductible and coinsurance, they have to send the claim to Medicare themselves, and they can't charge you for filing it (Medicare & You 2027; 42 CFR 424.55).

Non-participating providers still work with Medicare, but they haven't agreed to accept assignment for all services. They can take assignment claim by claim. When they don't, three things change: you might have to pay the whole bill at the visit, they can charge more than the approved amount (up to the limiting charge), and Medicare sends its share to you instead of to them (42 CFR 424.53(e)). They're still supposed to file the claim for you.

Opt-out providers have left Medicare for at least two years. Medicare pays nothing for their services except in an emergency or urgent care situation, the limiting charge doesn't apply, and you pay whatever the two of you agree to in a private contract. More on that below.

Source: Medicare & You 2027, pp. 64-65; Medicare.gov, Does your provider accept Medicare as full payment?; 42 CFR 424.55, 424.53, 405.425, 405.415; CMS, Choosing a Medigap Policy, 2026.

One more group to know about: some practitioners can't bill above the approved amount at all. Federal law requires physician assistants, nurse practitioners, clinical nurse specialists, certified registered nurse anesthetists, certified nurse-midwives and some others to bill Medicare on an assignment basis, and to collect nothing from you beyond the deductible and coinsurance (42 U.S.C. 1395u(b)(18)). So an excess charge from a nurse practitioner's visit is a red flag, not a normal bill.

The same goes if you have Medicaid or the QMB program. Physicians' services for people eligible for Medicaid can only be paid on an assignment basis (42 U.S.C. 1395w-4(g)(3)), and Medicare & You says providers aren't allowed to bill QMB members for Part A or B deductibles, coinsurance or copayments. If money is tight, the Medicare Savings Program in Washington post explains who qualifies.

The math: 95%, then 115%

Medicare's consumer pages say "in many cases" the limiting charge can't be more than 15% above the Medicare-approved amount. That's accurate, but it leaves out the step that matters. There are two approved amounts for the same service in the same area:

• The participating amount. The physician fee schedule amount, built from relative value units, a geographic adjustment and a conversion factor (42 CFR 414.20(a)).
• The non-participating amount. 95% of the participating amount (42 CFR 414.20(b); the statute is Social Security Act §1848(a)(3)). That 5% haircut is the federal incentive to participate.

The limiting charge is 115% of the non-participating amount (42 CFR 414.48(b); Social Security Act §1848(g)(2)(C)). So 1.15 × 0.95 = 1.0925. A non-participating doctor who doesn't take assignment can collect at most 9.25% more than a participating doctor would be allowed for the same service, not 15% more.

The rule also has teeth. Under §1848(g)(1), nobody is liable for any amount billed above the limiting charge. If a doctor bills over the cap, they have to cut the bill; if they've already collected it, they have to refund the difference, within 30 days of being notified by Medicare's contractor. Doctors who do it knowingly and repeatedly can be sanctioned (42 U.S.C. 1395w-4(g)(1)).

Two limits on the limit. Medicare.gov says the limiting charge only applies to certain Medicare-covered services and doesn't apply to some supplies and durable medical equipment, so a non-participating equipment supplier can cost you more (Medicare.gov). And an opt-out doctor isn't bound by it at all.

A worked example

Hypothetical, with round numbers. Say a specialist visit has a participating Medicare-approved amount of $100.00, and you've already met the $283 Part B deductible for 2026.

Participating doctor$100.00Non-participating, takes assignment$95.00Non-participating, no assignment (limiting charge)$109.25

Source: Maru Insurance calculation using 42 CFR 414.20(b) (95%) and 42 CFR 414.48(b) (115%).

Show the numbers

Item	Total allowed
Participating doctor	$100.00
Non-participating, takes assignment	$95.00
Non-participating, no assignment (limiting charge)	$109.25

Source: Maru Insurance calculation; rules from 42 CFR 414.20, 414.48, 424.53(e) and Medicare & You 2027 (20% coinsurance after the deductible).

Notice the middle column. A non-participating doctor who does take assignment on your claim is actually a little cheaper for you, because your 20% is figured on the lower $95.00 amount. The cost shows up only when they don't take assignment.

On a $100.00 visit, the excess is $14.25. Annoying, not ruinous. The problem is scale. Original Medicare has no yearly out-of-pocket limit, and the excess charge isn't capped by anything except the 115% rule. Run the same math on a surgery or a course of treatment and it grows in step:

$0.00$100.00$200.00$300.00$400.00

$200.00

$190.00

$332.50

ParticipatingTakes assignmentNo assignment

Source: Maru Insurance calculation using 42 CFR 414.20(b) and 414.48(b).

Show the numbers

	Your share
Participating	$200.00
Takes assignment	$190.00
No assignment	$332.50

At $1,000.00, the excess is $142.50 and your share goes from $200.00 to $332.50. And if the doctor didn't take assignment, you may have paid the full $1,092.50 at the front desk and be waiting for Medicare's $760.00 to arrive in the mail.

Which Medigap letters pay excess charges

Medigap policies in Washington use the federal standardized letters, and every policy with the same letter has the same basic benefits no matter who sells it. CMS's benefit chart shows only two letters paying the Part B excess charge, both at 100%: F and G.

Source: CMS, Choosing a Medigap Policy, 2026 (Product No. 02110), benefit chart. *Plan N pays the Part B coinsurance except for copays of up to $20 for some office visits and up to $50 for emergency room visits that don't lead to an admission.

What that means in the example above: with Plan G, after the $283 Part B deductible, both the $19.00 coinsurance and the $14.25 excess are covered. With Plan N, the coinsurance is covered apart from its office-visit copay, but the $14.25 excess is yours. With K or L, you'd pay part of the coinsurance and all of the excess.

A few cautions before anyone picks a letter over this one row:

• Plan F isn't open to everyone. People new to Medicare on or after January 1, 2020 can't buy C or F. For them, G is the only letter with excess-charge coverage (CMS guide).
• High-deductible F and G pay excess charges too, but only after you've paid up to $2,950 in 2026 in Medicare-covered costs (Medicare.gov).
• Medigap doesn't pay for services Medicare doesn't pay for. If you sign a private contract with an opt-out doctor, Medigap pays nothing, F and G included.
• Medicare Advantage is a different system. Excess charges are an Original Medicare concept. The trade-offs are in Medicare Advantage vs. Medigap in Washington.

Washington has one rule that softens this decision. Under RCW 48.66.045, someone who already has a Medigap plan B through N can switch to another B-through-N plan (other than C or F if you became eligible in 2020 or later) at any time, with no health questions. So a person with Plan N who finds their specialists don't take assignment can move to G later. The details and limits are in my Medicare Supplement in Washington post.

Does Washington limit excess charges?

Not that I could find. I looked for a Washington statute or Office of the Insurance Commissioner rule that bans or lowers Medicare Part B excess charges and found none. The state's Medigap law (RCW 48.66) regulates supplement policies, not what doctors may bill people on Medicare. So plan around the federal cap: 115% of the non-participating amount.

You'll see lists online of states that restrict excess charges. I couldn't confirm those lists against a CMS or Medicare.gov source, so I'm not repeating them here. If you split your year between Washington and another state, ask SHIBA or that state's SHIP whether the other state has its own rule.

Opt-out doctors and private contracts

Opt-out is a different animal from non-participation. An opted-out doctor or practitioner files an affidavit with Medicare and stays out for two-year periods that renew automatically unless they cancel. During that time Medicare pays nothing for their services, Medicare Advantage plans can't pay them either, and the limiting charge doesn't apply (42 CFR 405.425).

To see you, they need a written private contract signed before you're treated. Federal rules spell out what it has to say (42 CFR 405.415), and it's worth reading every line. It must state that:

• you accept full responsibility for paying their charges, and Medicare's limits don't apply;
• you won't submit a claim to Medicare, and Medicare won't pay even for services it would normally cover;
• Medigap plans don't pay for services Medicare doesn't pay for;
• you have the right to get the same Medicare-covered services from doctors who haven't opted out;
• whether the doctor has been excluded from Medicare, and the dates of the current opt-out period.

A private contract can't be signed while you need emergency or urgent care. If an opted-out physician treats you in an emergency without a prior contract, they have to bill Medicare and can collect no more than the limiting charge (42 CFR 405.440).

Medicare.gov suggests calling your SHIP before you sign a private contract. In Washington that's SHIBA. I'd add: get the expected total in writing first, because none of it will be reimbursed.

How to check a provider before you go

An excess charge is easiest to deal with before the visit, by asking first.

1. Use Care Compare. Medicare points people to Medicare.gov Care Compare to see whether a doctor accepts assignment or participates in Medicare. For equipment, Medicare.gov has a separate supplier directory.
2. Check the opt-out list. CMS publishes an opt-out affidavit lookup tool on data.cms.gov.
3. Ask the office directly, in these words: "Do you accept Medicare assignment for this service?" Not "Do you take Medicare?" A non-participating office can honestly say yes to the second question and still bill the limiting charge.
4. Ask again for each new provider. Surgery can involve an anesthesia provider, an assistant surgeon or a radiologist you never chose. Ask the scheduler who else will bill you.
5. Call 1-800-MEDICARE (1-800-633-4227; TTY 1-877-486-2048) or SHIBA if the online tools and the office don't agree.

If you think you were overbilled

The paper trail starts with your Medicare Summary Notice. It isn't a bill; it shows what was billed to Medicare, what Medicare paid and what you may owe. It comes in the mail at least twice a year, or monthly by email if you sign up, and your claims usually show up in your Medicare.gov account within 24 hours of processing (Medicare & You 2027).

Source: 42 U.S.C. 1395w-4(g); 42 U.S.C. 1395u(b)(18); Medicare & You 2027, pp. 63-65, 110; Medicare.gov; WA OIC, SHIBA; WA OIC, Report Medicare fraud.

For a denial, the steps and deadlines are in my Medicare appeal process guide. For one-on-one help, at no charge, reading an MSN or a confusing bill, SHIBA counselors do this every day: call 800-562-6900, 8:30 a.m. to 4:30 p.m., Monday through Friday, or see how SHIBA works in Washington.

About cost timing: the $283 deductible and $202.90 premium above are 2026 figures from CMS. As of November 3, 2026, CMS hasn't announced the 2027 Part B premium or deductible, and the Medicare & You 2027 handbook says the 2027 premium amounts weren't available when it went to print. The 95% and 115% rules don't change from year to year; they're written into federal law.

If you're weighing how excess charges fit into choosing a Medigap letter, our Washington Medicare Supplement page covers how supplements work with Original Medicare, and the Washington Medicare page covers the broader options.

FAQ

What is a Medicare Part B excess charge?

It's the difference between what a non-participating doctor who doesn't accept assignment bills you and the Medicare-approved amount. Federal law caps the total at 115% of the non-participating fee schedule amount, which itself is 95% of the participating amount.

Does Washington state allow Medicare excess charges?

I couldn't find a Washington statute or Insurance Commissioner rule that bans or lowers Part B excess charges, so the federal limiting charge is the cap to plan around.

Which Medigap plans cover Part B excess charges?

Among the standardized letters, only Plans F and G pay the Part B excess charge, at 100%. Plan F isn't available to people new to Medicare on or after January 1, 2020.

Can a doctor charge more than the limiting charge?

Not for a service the limiting charge applies to. Federal law says no one is liable for amounts billed above it, and anything collected over it must be refunded. Opt-out doctors with a private contract aren't bound by it, and it doesn't apply to some supplies and equipment.

Your own policy wording and federal and Washington law control. Confirm your situation with a licensed agent, SHIBA or the Washington Office of the Insurance Commissioner, or, for legal questions, an attorney.

Sources

1. 42 CFR 414.48: Limits on actual charges of nonparticipating suppliers (115%)
2. 42 CFR 414.20: Formula for computing fee schedule amounts (nonparticipating = 95%)
3. 42 CFR 424.55: Payment to the supplier (assignment terms)
4. 42 CFR 424.53: Payment to the beneficiary (unassigned claims)
5. 42 CFR 405.415: Requirements of the private contract
6. 42 CFR 405.425: Effects of opting out of Medicare
7. 42 CFR 405.440: Emergency and urgent care services (opt-out)
8. 42 U.S.C. 1395w-4 (Social Security Act §1848): limiting charge, refunds, Medicaid assignment
9. 42 U.S.C. 1395u(b)(18): mandatory assignment for certain practitioners
10. Medicare.gov: Does your provider accept Medicare as full payment?
11. CMS: Medicare & You 2027 handbook
12. CMS: Choosing a Medigap Policy, 2026 (Product No. 02110)
13. Medicare.gov: Compare Medigap plan benefits
14. CMS: 2026 Medicare Parts A & B premiums and deductibles fact sheet
15. Medicare.gov: Care Compare (doctors and clinicians)
16. CMS: Provider opt-out affidavits lookup tool
17. WA OIC: Report Medicare fraud (SHIBA and Senior Medicare Patrol)
18. RCW 48.66: Medicare supplemental health insurance act
19. RCW 48.66.045: Medigap switching without health questions
20. WA OIC: Get free Medicare help from SHIBA