How to Read a Medicare EOB for Billing Teams

To read a Medicare EOB as a provider, first confirm you hold the provider remittance, not the patient's notice. Then read each claim by its ICN, check the MOA remark codes, and follow every service line from billed to allowed, deductible, coinsurance, the sequestration reduction and the amount paid, using the group and reason codes on each line.

Medicare EOB vs Medicare Summary Notice: which one are you holding?

A "Medicare EOB" in a billing office almost always means the remittance advice a Medicare contractor sends the provider. The Medicare Summary Notice is a different document, sent to the patient. Before reading any numbers, check which one is on the desk, because the two are organized for different readers.

Chapter 22 of the Medicare Claims Processing Manual on remittance advice says the Medicare Administrative Contractors (MACs) send providers a remittance advice as a companion to claim payments, and that it explains the payment and any adjustments made during claim processing. The same chapter calls the paper version the Standard Paper Remittance (SPR) and describes it as the hard copy version of the electronic remittance advice.

The patient's document is described on Medicare's page about the Medicare Summary Notice. Medicare says it is not a bill, that people with Original Medicare get it in the mail, and that it lists the services billed to Medicare, what Medicare paid and the most the person may owe the provider.

Three quick signs tell them apart:

• The provider remittance groups many patients' claims under one payment, with a check or EFT number and a provider number on the first page.
• The Medicare Summary Notice covers one person and speaks to them directly.
• The remittance prints group codes such as CO and PR beside reason codes. The notice uses plain-language messages instead.

The general layout of any EOB, before the Medicare-specific fields, is covered in reading the EOB claim block.

Medicare remittance fields: ICN, MOA codes and reason codes

Medicare remittance fields follow one standard layout, so the same labels appear on every Part B paper remittance. Three matter most for reading a claim: the ICN, which identifies the processed claim; the MOA line, which carries claim-level remark codes; and the group and reason codes, which explain each adjustment on a line.

The field definitions below come from one MAC's published guide, Noridian's SPR field descriptions for Part B. Chapter 22 says all MACs use the paper format CMS established, so the labels carry over.

ICN. Noridian describes it as "The 13 digit Internal Control Number (ICN) identifies the processed claim." The first digits show the claim or adjustment type and the year. Quote the ICN when calling about a claim or appealing it, and store it with the posting. The stored ICN pays off later. When Medicare takes back or adds money on an old claim, the provider adjustment section of a later remittance shows a Financial Control Number (FCN), which Noridian says usually matches the ICN of the earlier claim. Without the stored ICN, that adjustment is hard to tie to anything.

NAME, MID and ACNT. These identify the patient. MID is the Medicare ID from item 1a of the CMS-1500, and ACNT is the practice's own patient account number from item 26. Noridian notes that a zero appears in ACNT if no account number was sent, which makes matching harder.

MOA. Noridian says Medicare Outpatient Adjudication (MOA) remark codes "are used to convey appeal information and other claim-specific information," with up to five per claim and none carrying a dollar adjustment. Chapter 22 gives MA01 as an example of an informational code, which tells the provider how to appeal if they disagree with what Medicare approved.

Group and reason codes. The GRP/RC-AMT column pairs a group code with a reason code and an amount. Chapter 22 defines CO, contractual obligation, as an adjustment from a contract or a regulatory requirement that is generally written off and not billed to the patient. PR, patient responsibility, is the amount the patient may be billed. What each group code means across payers is explained in what CO, PR, OI and PI group codes mean.

PT RESP and NET. Noridian gives the formula: PT RESP equals DEDUCT plus COINS plus any amounts under group code PR. NET is the net paid amount for the claim, including interest.

Remark codes as a code set, beyond the MOA line, are covered in where remark codes appear on paper EOBs and 835s.

How does sequestration show on a Medicare EOB?

Sequestration shows on a Medicare EOB as its own adjustment on each paid line, marked with reason code 253. It reduces what Medicare pays the provider after the deductible and coinsurance are worked out. It never raises what the patient owes, so the patient balance on the line is the same with or without it.

The reduction comes from a federal sequestration order. A 2013 CMS notice on Medicare fee-for-service sequestration said claims with dates of service on or after April 1, 2013 would incur a 2 percent reduction in Medicare payment. It also set the order of work: the adjustment "shall be applied to all claims after determining coinsurance, any applicable deductible, and any applicable Medicare Secondary Payment adjustments." The same notice says beneficiary payments for deductibles and coinsurance are not subject to the reduction.

CMS then created a dedicated reason code. Its transmittal creating CARC 253 replaced an older general code with 253, which the X12 Claim Adjustment Reason Codes list now names "Sequestration - reduction in federal payment."

Because the reduction is a regulatory adjustment the patient does not pay, it fits Chapter 22's definition of the CO group, and it is written off. Do not move it to the patient. Do not appeal it as an underpayment. Take the amount from the remittance itself rather than from a fixed percentage set in your system.

Medicare Part B deductible and coinsurance lines

Medicare Part B deductible and coinsurance lines show the patient's share of the allowed amount. The DEDUCT column holds any part of the annual deductible applied to the line. The COINS column holds the coinsurance, which for most Part B services is 20 percent of what remains of the allowed amount after the deductible.

CMS publishes the deductible each year. Its fact sheet on 2026 Medicare Part B premiums and deductibles says the annual Part B deductible is $283 in 2026, up from $257 in 2025. Early in the year, the deductible often appears on many lines until the patient has met it. Later in the year, the DEDUCT column is usually zero.

Noridian's field guide describes COINS as the amount the patient is responsible for and says it is generally 20 percent of the allowed amount, with most outpatient mental health services at 50 percent. ALLOWED, in the same guide, is the Medicare reimbursement rate for the service billed.

One Part B line, worked

This example follows one fictional office visit for a fictional patient, Ana Rivera, with example member ID 1EG4TE5MK72 and ICN 0226100123450. Every amount is made up. The sequestration rate is shown as 2 percent for the example.

The line balances: $180.00 billed minus $60.00, $20.00, $20.00 and $1.60 leaves $78.40 paid. Why the allowed amount sits below the charge, and how the patient share is built, is explained in allowed amount vs billed amount on an EOB.

Medicare crossover claims on the remittance

A Medicare crossover claim is one that Medicare forwards to the patient's secondary or supplemental insurer after it pays. On the remittance, a crossover shows as a remark code and, on paper, a line naming the payer that received the claim. When you see it, do not send that secondary claim yourself.

CMS runs crossover through a standard contract. Its page on the Coordination of Benefits Agreement says supplemental insurers send eligibility files to the Benefits Coordination and Recovery Center, which transfers claims to them in standard formats for the patients on those files.

Noridian's field guide describes the SPR field CLAIM INFORMATION FORWARDED TO, which names the supplemental insurer, and the message that goes with it: "The claim information is also being forwarded to the patient's supplemental insurer." The X12 Remittance Advice Remark Codes list carries this message as MA18. It also lists MA07, for claims also forwarded to Medicaid, and N89, for payment information forwarded to more than one other payer.

Chapter 22 adds a limit worth knowing. MACs report only one crossover payer name on the remittance, even when the claim goes to more than one payer, because the 835 has room for only one. If the patient has two supplemental plans, the second may not be named.

After a crossover, post the Medicare payment, leave the PR amount open, and wait for the secondary payment before billing the patient.

Medicare Advantage EOBs: when the Medicare layout does not apply

A Medicare Advantage EOB comes from a private health plan, not from a Medicare contractor, so the standard Medicare remittance layout does not apply. Expect the plan's own format, field names and claim numbers, read the way you would read a commercial EOB, even though the patient has a Medicare card.

Medicare's booklet Understanding Medicare Advantage Plans describes these plans as Medicare-approved plans offered by private companies that must follow Medicare's rules, and as another way to get Part A and Part B coverage. The plan processes the claim and sends the remittance.

That has three practical effects:

• There is no ICN in the Medicare sense. The plan's own claim number goes on appeals and calls.
• Deductibles and coinsurance follow the plan's benefit design, which may differ from the Original Medicare figures above.
• Crossover to a Medigap policy does not happen. The same booklet says Medigap cannot be used to pay Medicare Advantage copayments, coinsurance or deductibles.

Check the payer name on the first page before reading any numbers. If it is a commercial plan, the commercial reading order applies. Many offices key both Medicare and plan remittances by hand. Schema Care reads either kind of EOB into fields, each tied to its spot on the page, and the list of document types and fields it reads shows what it covers. For how a paper remittance compares with the electronic 835 file for posting, see the comparison of EOB vs ERA 835 differences, and for patient bills and claim forms, the claims and medical bills category.