CARC and RARC: What the Codes on Your EOB Actually Mean

One line on your EOB, near the bottom of the third page, in a column narrow enough that nothing fits:

PR-96    N130    $1,412.00

Nobody explains those codes. The letter that came separately, if one came at all, says the service was not covered. The hospital's statement says you owe $1,412. Connecting those two facts is a number, a letter-and-number, and two capitals that most people read as an abbreviation for something.

They are not an abbreviation. They are entries from three separate published lists, each with its own rules about what it may and may not be used to say. Once you know which list you are reading, the line stops being a code and becomes a claim somebody made about your money.

Everything below was read on the source pages on 22 August 2026.

Three lists stacked into one column

The 96 is a claim adjustment reason code, a CARC. X12 describes the list in one sentence: these codes "describe why a claim or service line was paid differently than it was billed" (X12, Claim Adjustment Reason Codes). A CARC always attaches to a dollar amount. It is the accounting explanation for a gap between what was charged and what was paid.

The N130 is a remittance advice remark code, a RARC, and it comes from a different list entirely. In full it reads "Consult plan benefit documents/guidelines for information about restrictions for this service" — which is the whole of what the plan said about why. Its job is subordinate. RARCs exist "to provide additional explanation for an adjustment already described by a Claim Adjustment Reason Code (CARC) or to convey information about remittance processing" (X12, Remittance Advice Remark Codes). That same page splits RARCs into two types worth telling apart. Supplemental RARCs explain an adjustment a CARC already named. Informational ones are all prefaced with Alert: and, in X12's words, "are never related to a specific adjustment or CARC." An Alert on your EOB is therefore not the reason for anything. It is a notice riding along.

The PR comes from a third list, the claim adjustment group codes — the shortest list and the one that decides the most. X12 gives it a single line of explanation — "These codes categorize a payment adjustment" — and then prints the entire list: CO, Contractual Obligation; OA, Other Adjustment; PI, Payor Initiated Reduction (X12's spelling); PR, Patient Responsibility. Four entries, each carrying a start date of 05/20/2018, nothing under Deactivated, and the page last updated 5/20/2018. Older billing material adds a fifth, CR; the current list does not carry it at all, which is worth knowing before you go hunting for it. Two letters, and they separate an amount a provider already agreed to write off from an amount you can be billed for. That distinction has enough moving parts to need its own treatment. Here, just record which of the four sits in front of your number.

Scale, so you know what you are searching: on 22 August 2026 the CARC list carried 297 current codes and 110 deactivated ones, the RARC list 1,137 current and 79 deactivated. Both pages date themselves — the CARC list was last updated 11/1/2025, the RARC list 7/1/2026.

Some codes are not allowed to travel alone

This is the most useful structural fact on the list.

A handful of CARCs carry a usage note that is not advice but a requirement. Code 16 — "Claim/service lacks information or has submission/billing error(s)" — carries this: "At least one Remark Code must be provided (may be comprised of either the NCPDP Reject Reason Code, or Remittance Advice Remark Code that is not an ALERT.)" Code 96, plain "Non-covered charge(s)," carries the same sentence. So do 227, 252 and A1 — fifteen current codes in all on 22 August 2026. Code 17 carries a near-identical sentence and turns up in older billing guides for that reason, but it was stopped on 1 July 2009 and has no business on a current remittance.

Read what that does to the paper in front of you. Code 96 alone identifies nothing — it says a charge was not covered, which you already knew from the balance. The code naming the reason is the remark code the list requires to accompany it. A bare 96 with an empty remark column is an explanation incomplete by the code set's own rule, which is quotable and fits in one sentence of a letter.

The other half of that parenthetical matters too. NCPDP reject reason codes are a different set again, used on pharmacy claims. If your denial concerns a drug at a retail counter, your number may not be on either X12 list at all.

What the ones you keep seeing actually say

Published descriptions, quoted from the X12 lists as they stood on 22 August 2026. The right-hand column is the part that matters.

Two of those rows deserve a pause, because they are where patients most often pay money they never owed.

197. A missing prior authorization is a failure under a contract, and that contract is usually between the provider and the plan rather than between you and anyone. Whether the amount can be shifted onto you turns on the group code and the provider's network agreement, not on the number.

29. If the provider filed too late, the plan pays nothing, and the resulting balance is very often not billable to the patient under the provider's own contract. A statement that surfaces months later with this code behind it earns one specific question to the billing office before any payment.

Two habits keep these codes honest. Match every code line to a line on the itemized bill, which means asking for the itemized bill first, since summaries hide the line that is actually wrong. And keep the EOB beside the denial letter, because the letter is where the enforceable requirements land.

When the code and the letter say different things

Sooner or later they will. The determination is the letter. The federal rule governing a denial notice for non-grandfathered coverage requires "the denial code and its corresponding meaning, as well as a description of the plan's or issuer's standard, if any, that was used in denying the claim" (45 CFR 147.136(b)(2)(ii)(E)(3), read 22 August 2026). Look at the shape of that sentence. The code is required to be in the notice; the code is not itself the explanation. The plan's standard is listed as a separate item, and so is the specific reason and the plan provision the Labor Department rule demands.

So the code is evidence about how a claim was processed; the notice is the decision. When the two diverge, quote both and ask the plan to reconcile them in writing.

Three specific mismatches recur often enough to name.

A code that no longer exists. Codes get retired. CARC 38, "Services not provided or authorized by designated (network/primary care) providers," was stopped on 1 January 2013, and the list carries a note that codes 242 and 243 replace it. A deactivated code on a recent remittance points at a system problem rather than a coverage decision.

An Alert read as a rule. RARC MA02 says: "Alert: If you do not agree with this determination, you have the right to appeal. You must file a written request for an appeal within 180 days of the date you receive this notice." Useful, and not a deadline to rely on. It is generic list text. Someone with Original Medicare has 120 calendar days from receipt of the Medicare Summary Notice to request a redetermination under 42 CFR 405.942(a), and the levels above that one run on their own clocks. Take the date from your notice and from the rule that governs your coverage. Never from a remark code.

A policy the code points at that your copy does not contain. Dozens of CARC entries end with "Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present." That segment carries the payer policy behind the adjustment, and it lives in the 835 electronic remittance advice — the payer-to-provider transaction adopted as a HIPAA standard at 45 CFR 162.1602. Your EOB is a consumer-facing rendering. The 835 is the original, and it went to your provider.

Which hands you a document almost nobody thinks to ask for: the remittance advice your provider received on your claim. Billing records held by a provider sit inside the designated record set defined at 45 CFR 164.501, and the HIPAA right of access at 164.524 obliges a covered entity to act on a written request within 30 days, with one 30-day extension if it tells you in writing why. Ask by date of service, for the remittance advice and any payer policy identifier tied to the claim.

Looking the code up yourself, on the list that governs it

Do this before you write anything, because the code text on a billing vendor's blog is frequently a paraphrase, occasionally a retired version, and never dated.

Start at x12.org/codes and pick the right list. Claim adjustment reason codes for the number. Remittance advice remark codes for the letter-and-digits. Claim adjustment group codes for the two capitals in front. X12's own CARC page opens by anticipating your exact situation — "Did you receive a code from a health plan, such as: PR32 or CO286?" — so you are not in the wrong place.

Then use the status filter, the step separating a current answer from a wrong one. Each list can be filtered to Show All, Current, To Be Deactivated, or Deactivated, and every entry carries its own dates: a Start date, a Last Modified date wherever the wording was revised, a Stop date where the code was retired. Check yours against the date of service on your EOB. A code modified in 2018 meant something else in 2013, and a code with a stop date has no business on a 2026 remittance.

Copy the description verbatim, with the date you read it, into your file on this claim. Verbatim matters. Paraphrase is how "not deemed a 'medical necessity' by the payer" becomes, three letters later, an admission that the care was unnecessary.

One note on where these lists live, because it explains a lot of dead links. The regulation adopting the 835 standard still names Washington Publishing Company as publisher of the technical reports, and for years washingtonpublishing.com was where everyone went for the codes. On 22 August 2026 that domain had name servers but no address record — it resolved to nothing, and every article still pointing there sends you into a void. X12 hosts the lists now.

They also move on a published schedule. CMS issues a recurring update to the CARC and RARC sets for its contractors every quarter, and two of them are live documents at any moment. The update in effect on 22 August 2026 is Transmittal 13666 (Change Request 14410, dated 25 March 2026), effective 1 July 2026 (CMS, R13666CP). Its successor is already published: Transmittal 13791 (Change Request 14492, dated 27 May 2026), effective 1 October 2026, implementation 5 October 2026 (R13791CP). If your claim straddles one of those dates, read the entry's Last Modified line before assuming the wording you found is the wording that applied.

Nothing here is medical or legal advice; I read code lists and claim rules, and I have never billed a claim for a living. A code is a payment category, never a statement about your health. What it is, once you look it up properly, is a dated sentence written by a committee, sitting next to a dollar amount somebody assigned to you. Both are checkable. Start with the one on your line.