GRP/RC-AMT on a Medicare Remittance: Group Codes, Reason Codes and Amounts Explained

GRP/RC-AMT is the column on a Medicare remittance advice where every adjustment to a service line is shown as three things: the group code (who is responsible for the difference), the reason code (why the payer adjusted the charge), and the amount in dollars. A line reading CO-45 338.24 means the payer reduced the charge by 338.24 as a contractual obligation because the billed charge exceeded the fee schedule.

If you have ever looked at that column and wondered where the money went, you are not alone. It is the question new billers ask us most. Once you can read the three parts, the rest of the remittance is easy to follow.

Where you see it

GRP/RC-AMT appears on the Medicare Standard Paper Remittance (SPR) and in the printed version of the electronic remittance advice (ERA, the 835 transaction) that your practice management system produces. Commercial payers use the same group and reason codes on their EOBs, usually in a column labelled “Adjustment” or “Reason”. Every code is a national standard: the group codes and reason codes are published by X12 as the Claim Adjustment Reason Codes (CARC) and the remark codes as the Remittance Advice Remark Codes (RARC), so CO-45 means the same thing from Medicare, Aetna or Blue Cross. CMS explains the layout of the Medicare remittance itself in Remittance Advice Resources and FAQs from the Medicare Learning Network.

The sample below is a one-claim radiation oncology remittance from a Medicare contractor. The numbers in the image match the walk-through that follows.

1. CHECK/EFT is the payment this remittance explains. Post everything on the page against this one deposit.
2. HIC, ACCT and ICN identify the patient (Medicare Beneficiary Identifier), your account number for the visit, and the payer’s internal control number for the claim. You need the ICN for any appeal or reopening.
3. BILLED is what you charged.
4. ALLOWED is the fee schedule amount for the code, place of service and modifier.
5. GRP/RC-AMT, the column this article is about. Here: CO-45 338.24.
6. CO-253, the sequestration reduction.
7. COINS is the 20 percent coinsurance the patient owes on the allowed amount. The claim-level PT RESP adds the coinsurance and deductible for every line.
8. PROV PD is what Medicare paid for the line; NET is the claim total after interest and late-filing charges.
9. MOA and REM codes (MA01, MA18, N807) are remark codes that explain rather than adjust: appeal rights, crossover forwarding, and the MIPS adjustment.
10. CLAIM INFORMATION FORWARDED TO means Medicare sent the claim to the patient’s supplemental insurer automatically. Do not bill the secondary yourself; wait for the crossover.

The three parts of every adjustment

Group code: who is responsible

Group	Meaning	Can you bill the patient?
CO	Contractual Obligation: the provider’s write-off under its contract or, for Medicare, the law	No
PR	Patient Responsibility: deductible, coinsurance, copay, non-covered services the patient agreed to	Yes
OA	Other Adjustment: neither party is liable, for example a duplicate or a coordination-of-benefits situation	Usually no
PI	Payer Initiated Reduction: the payer reduced payment for a reason that is not contractual and not the patient’s, often pending review	No, pending appeal

The group code is the one that matters for your accounts receivable. CO goes to the contractual adjustment account. PR moves the balance to the patient. OA and PI need follow-up.

Reason code: why

The reason code is a number from the national Claim Adjustment Reason Code (CARC) list. The ones you will see most on a radiation oncology remittance:

Code	Meaning	What to do
45	Charge exceeds the fee schedule or contracted amount	Nothing; this is the normal fee-schedule write-off
253	Sequestration, the 2 percent federal reduction, applied after deductible and coinsurance (Noridian’s explanation)	Nothing; it cannot be billed to anyone
144	Incentive adjustment (MIPS)	Nothing; negative means you were paid more
1	Deductible amount (always with PR)	Bill the patient
2	Coinsurance amount (always with PR)	Bill the patient, or the secondary if there is one
3	Copayment amount (always with PR)	Bill the patient
4	Procedure code inconsistent with the modifier	Check the modifier and resubmit a corrected claim
16	Claim lacks information needed for adjudication	Read the remark code that comes with it, fix, resubmit
18	Duplicate claim	Find the original; do not resubmit
29	Time limit for filing has expired	Appeal only with proof of timely filing
50	Not medically necessary	Appeal with documentation, or write off
96	Non-covered charge	Check the remark code; may be billable to the patient with an ABN
97	Payment included in another service already adjudicated	Bundled; check NCCI edits before appealing
119	Benefit maximum reached	Bill the patient or the secondary
197	Precertification or authorization absent	Obtain retro-authorization if the payer allows, otherwise appeal

Amount

The dollar figure for that adjustment. The amounts for one service line, together with the deductible and coinsurance, always reconcile billed to paid.

Worked example: line 1 of the sample

Service: CPT 77370, special medical radiation physics consultation, modifier Q6 (locum tenens physician), place of service 11, date of service 05/22/2025.

Step	Amount	Where it comes from
Billed	467.00	your charge
less CO-45 contractual adjustment	338.24	billed minus allowed
Allowed	128.76	fee schedule
less coinsurance (PR-2, shown in COINS)	25.75	20 percent of 128.76
less CO-253 sequestration	2.07	2 percent of 103.56 (the 80 percent Medicare share of 103.01 plus the 0.55 MIPS incentive)
plus CO-144 MIPS adjustment	0.55	positive incentive, shown as -0.55
Provider paid	101.49	matches PROV PD

So of 467.00 billed, 338.24 is written off under CO, 25.75 is billed to the patient (or sent to the crossover payer), 2.07 is lost to sequestration, and 101.49 arrived in the EFT. Every line on every remittance reconciles this way. If your posting does not balance, compare it with the remittance to find the number you missed. The second line, 77014, follows the same pattern: 325.00 billed, 219.54 CO-45, 105.46 allowed, 21.09 coinsurance, 1.70 sequestration, 0.45 MIPS, 83.12 paid. Claim totals: 792.00 billed, 234.22 allowed, 46.84 patient responsibility, 184.61 paid.

What to do with each group when you post

• CO amounts post to contractual adjustments. If a CO reason code is anything other than 45, 253 or 144, it means something went wrong with the claim (modifier, bundling, medical necessity), and the line belongs on a work list, not in the write-off account.
• PR amounts move to patient or secondary balance. When MA18 says the claim was forwarded, hold the patient statement until the crossover payer responds.
• OA and PI amounts are never routine. Each one needs a person to decide whether to correct, appeal or write off.

A habit worth building: before you post any remittance, scan the GRP/RC-AMT column for anything that is not CO-45, CO-253, CO-144 or a PR code. Those few lines are the ones the practice may not get paid for, and they are easy to miss in a page of routine adjustments.

In Iridium Suite the ERA posts automatically and each adjustment posts to the right account by group code; lines with non-routine reason codes are routed to the denial work list instead of being written off, which is the step most practices miss when posting by hand. (One sentence, linked to the Accounts Receivable feature page.)

Related terms

• Explanation of benefits (EOB) versus remittance advice (ERA)
• PR-1, PR-2 and PR-3: deductible, coinsurance and copay
• Allowed amount, billed amount and write-off
• Remark codes: MA01, MA18, N807 and the other explanations
• Sequestration on Medicare claims
• Medicare crossover claims