CARC and RARC Codes 2026 (CO, PR, OA, PI)

Read the Remit Like a Biller, Not a Bystander

By Yagnesh Dave  ·  October 3, 2026  ·  12 min read

A practice with 1,500 claims a month and a 10% denial rate sees 150 denials. If 60% of those are fixable (a missing modifier, a duplicate, the wrong payer) and the average claim is $140, that's $12,600 a month sitting in the remit waiting for someone to read it correctly. Most of it never gets worked, because the code on the remittance looked like noise.

CARC and RARC codes are the language of the remit. A claim adjustment reason code tells you why the payer paid less than you billed. A remittance advice remark code adds the detail: what's missing, whether you can appeal, or which policy applied. Read them as a pair and the next step is usually obvious.

Here's how the 835 is built, what the group codes mean, the CARC and RARC pairs that drive most denials, and a routing table that sends each one to the person who can fix it.

How CARC and RARC Codes Work on the 835 Remittance

Your electronic remittance advice (the 835) reports every adjustment between what you billed and what the payer paid. Each adjustment sits in a CAS segment with three parts: a group code, a CARC and an amount.

The math has to balance. Billed charges minus all adjustments equals the payment. If a payer cuts $60 for a fee schedule difference and $20 for a patient deductible on a $200 charge, the payment is $120, and the remit shows two adjustments that add up to the $80 gap. When the numbers don't tie out, someone made a posting error or a payer sent a provider-level adjustment you haven't found yet.

RARCs ride along in separate segments and give you the detail. A CARC tells you "this was denied for missing information." The RARC tells you which information, and whether you can appeal. X12 maintains both lists and publishes updates three times a year, so a code you saw last spring might have a new meaning or a retired status.

Group Codes: CO, PR, OA, PI and CR

The group code is the first thing to read, because it tells you who owns the money. Reason code and group code travel together, and the same CARC can mean very different things depending on the group.

Never post a CO adjustment to a patient balance. It's the single most common patient billing error in medical offices, and it can get a practice into trouble with payer contracts and state billing laws.

Twelve CARC and RARC Codes That Drive Most Denials

You'll see a short list of reason codes over and over. Learn these first and you'll know what's happening with most of your remits.

Two RARCs deserve their own mention. MA130 means the claim was unprocessable because of incomplete or invalid information, and it carries no appeal rights. Submit a new claim instead of appealing. N290 flags a missing or invalid rendering provider identifier, which is one of the most common reasons for a CARC 16.

Routing CARC and RARC Denials to the Right Worklist

Reading codes isn't enough. Each one needs an owner and a deadline, or it sits until it's too old to fix. A simple routing rule set does most of the work.

Set an aging target for each queue. Fixable front-end denials should be corrected within a week. Appeals should be filed within 30 days of the denial so you've still got time on the payer's clock. A denial that sits for 90 days is a write-off in disguise.

Provider-Level Adjustments: The Part of the Remit Nobody Reads

At the bottom of an 835 sits the PLB segment, which holds adjustments that aren't tied to a single claim. A reason code of WO means an overpayment recovery, where the payer is taking back money from this remittance. FB means a forward balance, where the payer owes a negative amount carried to the next payment. L6 means interest owed.

These adjustments make a deposit look wrong. If a payer sends $9,400 against claims totaling $11,000 and the difference isn't in any CAS segment, check the PLB first. A $1,600 recoupment hiding there is a common reason the bank deposit and the posted payments don't match.

Never ignore a WO. It's the payer telling you it found an overpayment, and it starts a clock on your response. Read the attached notice, check whether the recoupment is correct, and file a dispute or return the correct amount promptly.

Appeal Deadlines After a CARC Denial

Appeal clocks start when the denial is issued, not when you read it. For Original Medicare, you have 120 days from receipt of the initial determination to request a redetermination, and Medicare presumes receipt 5 days after the notice date. Commercial payers set their own, commonly 90 to 180 days, and the number is in your contract.

Not every code is appealable. A denial paired with MA130 isn't, because the claim never processed. A CO-16 with a clear missing-data RARC should be corrected, not appealed. Appeals are for CO-50, CO-197 and other cases where the payer reviewed the claim and disagreed.

When you do appeal, quote the CARC and RARC in the first line. A reviewer who sees the codes you're contesting can find the right policy and the right claim line quickly.

Remittance Audit and Overpayment Exposure

The remit is also your audit trail. CMS's fiscal year 2025 data puts the Part B provider improper payment rate at 8.44%, or $9.62 billion, and insufficient documentation drove about 53% of improper payments across Medicare fee-for-service. When a contractor recoups money, the PLB WO segment on your remittance is the first notice.

Keep each remittance, the matching bank deposit and your posted payments together for at least six years, which aligns with the 60-day rule's lookback. When a reviewer or a payer questions a claim from three years ago, a reconciled remit is how you prove what was paid.

Medicare contractors can reopen a claim within 1 year for any reason and within 4 years for good cause. If your posting practice left a duplicate payment or a recoupment unreconciled, it can surface in that window and become something you owe.

Frequently Asked Questions About CARC and RARC Codes

What does group code CO mean on a remittance?

CO means contractual obligation. The provider is responsible for the adjusted amount and can't bill the patient for it. Fee schedule write-offs (CARC 45) and most front-end denials carry CO.

What's the difference between a CARC and a RARC?

A claim adjustment reason code (CARC) explains why the payment differs from the billed amount. A remittance advice remark code (RARC) adds detail, such as what to correct or whether appeal rights exist. They usually appear as a pair.

What should I do with CARC 16 and RARC MA130?

Don't appeal. MA130 tells you the claim was unprocessable because of incomplete or invalid information and carries no appeal rights. Fix the data and submit a new claim.

How long do I have to appeal a Medicare denial?

You have 120 days from receipt of the initial determination to request a redetermination. Medicare presumes you received the notice 5 days after its date.