An explanation of benefits arrives looking exactly like a bill, which is why so many people pay it. It has a dollar amount, a provider name, and a due-date energy about it. It is not a bill, and paying off an EOB is one of the more common ways to send money to the wrong place.
This guide walks the actual fields on a real published document: the sample explanation of benefits CMS distributes as Publication 11819, “Reading Your Explanation of Benefits (EOB),” revision date May 2022, linked from the agency’s medical bill rights pages. Every figure below comes off that sample, which is current as of September 2026. Your insurer’s layout will look different. The columns will not.
What Is an Explanation of Benefits
An EOB is your health plan’s written accounting of one claim. After a provider bills your insurer, the insurer processes the claim and sends you a statement showing what happened to it: what was charged, what the plan agreed to pay, what it actually paid, and what is left over for you.
CMS’s description is short and worth memorizing. An EOB “shows you the total charges for your visit” and “helps you understand how much your health plan covers, and what you’ll pay when you get a bill from your provider.” The CMS sample prints “THIS IS NOT A BILL” in the header block, directly under the statement date.
Three things follow from that. The EOB comes from your insurance company, not the provider. It arrives before the provider’s bill in most cases, sometimes weeks before. And it does not know what you have already paid, which is why the CMS sample carries an explicit warning that payments you made directly to the provider “may not be subtracted from this amount.”
How to Read It Line by Line
The CMS sample splits the claim detail table into three labeled groups: “What your Provider Can Charge You,” “Your Responsibility,” and “Total Claim Cost.” Here is every field, in the order it appears.
Claim number and date paid. A reference number for this specific claim. You need it for every phone call about the bill. Write it on the provider’s statement when it arrives.
Payee. Who receives money back if the claim was overpaid. Usually the provider. If it says your name, a refund may be coming to you.
Line number and date of service. Each service gets its own row. Two visits on the same day produce two rows. Check the dates against your own calendar first, because a date you do not recognize is the cheapest fraud check you will ever run.
Service description. Plain-language labels like “Medical care,” “lab test,” or “screening.” The CMS sample uses “Medical care” for both lines. This field is deliberately vague on most EOBs, which is exactly why you need an itemized bill from the provider to know what was actually done.
Claim status. Paid, denied, or pending. A status other than “Paid” is the field that should stop you.
Provider charges. The amount your provider billed. CMS: “the amount your provider bills for your visit.” This is a list price, and on most claims it is the largest and least meaningful number on the page.
Allowed charges. CMS: “the amount your provider will be paid; this may not be the same as the Provider Charges.” HealthCare.gov defines the allowed amount as “the maximum amount a plan will pay for a covered health care service,” also called the eligible expense, payment allowance, or negotiated rate. This is the number every other calculation runs off.
The plan discount. Not always its own column. On the CMS sample there is no discount column at all: the write-off is simply the gap between provider charges and allowed charges, explained by a remark code. Other insurers print it as “Plan discount,” “Provider write-off,” or “Amount not covered by contract.”
Copay. A flat fee set by your plan. On the sample, $35.00 on the second line.
Deductible. The portion of the allowed amount applied to your annual deductible. Zero on the sample, meaning this member had already satisfied it or the service was not deductible-eligible.
Coinsurance. Your percentage share of the allowed amount. Zero on the sample. See copay vs coinsurance for which one your plan uses where.
Paid by insurer. CMS: “the amount your health plan will pay to your provider.”
What you owe. CMS: “the amount you owe after your insurer has paid everything else.” Some plans label it Patient Balance or Patient Responsibility. This is the only number on the EOB that is ever payable, and even then you pay it to the provider, not to the plan.
Remark code. CMS: “a note from the health plan that explains more about the costs, charges, and paid amounts for your visit.” Usually two or three letters and numbers, defined in a legend at the bottom of the page. On the sample, code PDC reads: “Billed amount is higher than the maximum payment insurance allows. The payment is for the allowed amount.” Denial reasons live in this column too, which makes it the most important small print on the page.
What It Costs You
Here is the CMS sample EOB’s own claim detail, reproduced exactly. Two lines from one date of service, March 20, 2022.
| Line | Provider charges | Allowed charges | Copay | Deductible | Coinsurance | Paid by insurer | What you owe | Remark |
|---|---|---|---|---|---|---|---|---|
| 1: Medical care | $31.60 | $2.15 | $0.00 | $0.00 | $0.00 | $2.15 | $0.00 | PDC |
| 2: Medical care | $375.00 | $118.12 | $35.00 | $0.00 | $0.00 | $83.12 | $35.00 | PDC |
| Total | $406.60 | $120.27 | $35.00 | $0.00 | $0.00 | $85.27 | $35.00 |
Source: CMS Publication 11819, sample explanation of benefits.
Read what that actually says. The provider asked for $406.60. The plan’s negotiated allowed amount for the same care was $120.27. The gap, $286.33, is 70% of the billed charge, and it vanishes: an in-network provider contractually agreed to accept the allowed amount, so nobody pays it. Of the $120.27 that is real money, the plan paid $85.27 and the patient owed $35.00, which is one flat copay.
Two lessons sit in that table.
The billed charge tells you almost nothing about your cost. On line 1, a $31.60 charge produced a $2.15 allowed amount, a 93% write-off, and the patient owed nothing. Panic at the billed number and you will worry about the wrong claim.
Your exposure is built from the middle columns, not the first one. Copay plus deductible plus coinsurance equals what you owe. If the deductible column is large, that is because you have not met your deductible yet and the plan is passing you the full allowed amount. If the coinsurance column is large, the allowed amount was large. Either way, it all counts toward your out-of-pocket maximum for in-network covered care.
The write-off only works in network. When a provider has no contract with your plan, there is no agreement to absorb that gap, and the provider may bill you for it. That is balance billing, and the CMS uniform glossary gives the mechanics: “if the provider’s charge is $200 and the allowed amount is $110, the provider may bill you for the remaining $90.”
EOB vs the Provider’s Bill
| Explanation of benefits | Provider’s bill | |
|---|---|---|
| Who sends it | Your health plan | The doctor, hospital, or lab |
| Is it a request for money | No | Yes |
| Shows the billed charge | Yes | Yes |
| Shows the allowed amount | Yes | Usually not |
| Shows what the plan paid | Yes | Sometimes, as “insurance payment” |
| Shows what you already paid | No | Yes, usually |
| Shows denial and remark codes | Yes | Rarely |
| Arrives first | Usually | Usually second |
| What you do with it | File it, check it | Pay it, after checking it against the EOB |
The single rule that connects the two documents comes straight from CMS: your bill should not be higher than the patient balance on the EOB. If it is, something is wrong on one of the two pieces of paper.
If You Have Original Medicare, You Get an MSN Instead
Original Medicare does not send EOBs. It sends a Medicare Summary Notice, and Medicare.gov states it “is not a bill” and arrives at least twice a year, every 6 months, if you had any services in that period. Medicare publishes annotated samples for Part A, Part B, and durable medical equipment.
The Part B sample uses different column names for the same ideas: what the provider charged, what Medicare approved, what Medicare paid, and a bolded “Maximum You May Be Billed.” That last column is the MSN’s version of patient responsibility, and it is a ceiling, not an invoice. The sample also flags whether each claim was assigned or unassigned, which matters because unassigned claims are where Medicare’s limiting charge comes into play. Page 4 of the sample is entirely about denied claims and states you have 120 days to appeal. See Medicare appeal for how that runs.
Medicare Advantage plans do send EOBs, monthly, and they read like commercial EOBs.
What to Do When the EOB and the Bill Disagree
Work in this order. It takes about twenty minutes and it is the highest hourly rate most people will ever earn.
1. Match claim numbers and dates. Pull the claim number off the EOB and find the same one on the provider’s statement. Mismatched dates of service are the most common cause of a bill that does not tie out.
2. Get an itemized bill. The EOB says “Medical care.” The itemized bill says which CPT codes were billed. You cannot dispute a charge you cannot see. Our guide to requesting an itemized hospital bill has the script.
3. Compare the bill total to the patient responsibility column, not to the billed charge. If the provider is billing you the difference between their charge and the allowed amount on an in-network claim, that is a contractual write-off being billed to you in error. Say those words on the phone.
4. Read the remark code. If a line was denied, the code says why. KFF’s analysis of 2024 marketplace data, published in March 2026, found insurers denied roughly 85 million of 451 million in-network claims, an average in-network denial rate of 19%, and 37% for out-of-network claims. The stated reasons skew toward paperwork rather than medicine: 36% were coded “other,” 25% administrative, 13% excluded service, 9% missing prior authorization or referral, and only 5% medical necessity. A denial is frequently a coding or routing problem the provider’s billing office can refile.
5. Appeal if the denial stands. KFF found that fewer than 1% of denied marketplace claims were appealed in 2024, roughly 262,982 internal appeals against 85 million denials, and insurers overturned 34% of the ones they did receive. Roughly a third of the appeals nobody files would have worked. Start with how to appeal a health insurance denial and use the insurance appeal letter template.
6. If the bill is out-of-network and unexpected, check your protections first. Federal law blocks most surprise out-of-network bills for emergency care and for out-of-network clinicians working at in-network facilities. See the No Surprises Act and in-network vs out-of-network.
7. Only then negotiate what is genuinely owed. Once the number is verified, it is a normal medical bill and normal tactics apply: see how to negotiate medical bills.
The Bottom Line
An EOB is a receipt for a transaction between your provider and your insurer, and you are cc’d. Ignore the billed charge, which is a list price. Ignore the allowed amount except as a sanity check on the discount. Look at the patient responsibility column, confirm it was built from a copay, deductible, or coinsurance you recognize, and then wait for the provider’s bill to see whether it matches.
If it does not match, the EOB is your evidence, and CMS’s own standard is that the bill should not exceed the patient balance. If a line was denied, the remark code is your starting point, and the odds on appeal are far better than the 1% appeal rate suggests. Keep every EOB for at least a year. It is the only document that shows what your plan agreed a service was worth.