PR-4 Denial Code: Procedure Code Inconsistent With the Modifier

PR-4 is Claim Adjustment Reason Code 4 with group code PR. CARC 4 means the procedure code is inconsistent with the modifier used. A modifier is a two-character code added to a procedure code to give more detail about the service. The payer found that the modifier does not fit the code, and it placed the amount under patient responsibility. That pairing is unusual, so read it with care before you bill anyone. Many people search for “pr 4 denial code”, and that is the phrase this page answers. (Primary sources: X12 Claim Adjustment Reason Codes · CMS Claims Processing Manual, Ch. 22, §60.1 · CMS Claims Processing Manual, Ch. 12, §30.6.6)

Quick answer: The reason in PR-4 is a coding problem, but the group says the patient may owe the amount. Fix the modifier and resubmit first. Then ask the payer why a modifier error was placed in the PR group. Do not send a patient statement until the payer confirms the amount is a real patient share.

Part of our denial codes library. Written by Manikandan, a revenue cycle management specialist with more than 10 years of US medical billing experience. Last reviewed: 16 October 2026. Official code wording is quoted word for word from X12; Medicare rules link to their CMS source.

PR-4 denial code description (official X12 wording)

X12 Claim Adjustment Reason Code 4, verbatim:

“The procedure code is inconsistent with the modifier used. Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.”

Source: X12 Claim Adjustment Reason Codes, checked 16 October 2026. Start: 01/01/1995. Last Modified: 03/01/2020.

The CARC is 4. Here the group code is PR. CMS describes PR as the group code used “when the adjustment represent an amount that may be billed to the patient or insured. This group would typically be used for deductible and copay adjustments.” CMS Transmittal 470 (2005) lists CARC 4 with group code CO, not PR, for Medicare fiscal intermediaries.

What PR-4 means in plain English

• The modifier and the procedure code do not fit. The payer’s edit rejected the pair.
• The group is PR. The remit says the patient may be responsible for the amount.
• That is not the usual group for this reason. A modifier error is a billing issue, and CMS describes PR as typically used for deductible and copay adjustments.
• Do not assume the patient owes it. Ask the payer to confirm what the PR amount is.
• Fix the claim first. A corrected claim may remove the adjustment.

PR-4 vs CO-4, N519 and lookalikes

Code	Official X12 idea	What it tells you
PR-4	Procedure code inconsistent with the modifier used	Modifier error filed to the patient group. This page
CO-4	Same reason, group CO	Provider write-off path. See CO-4
N519	Invalid combination of HCPCS modifiers	RARC for an invalid modifier combination
PR-1	Deductible amount	A true patient share. See PR-1, PR-2, PR-3
CO-16	Claim/service lacks information or has submission/billing error(s)	Missing or bad data. See CO-16
CO-11	Diagnosis inconsistent with the procedure	Dx vs service. See CO-11

How modifier rules reach a claim

CMS Claims Processing Manual Ch. 26, Item 24D says to “show HCPCS code modifiers with the HCPCS code” and that the CMS-1500 can capture up to four modifiers. A payer edit checks each modifier against the code it follows.

Some rules are public. CMS Ch. 12, §30.6.6 B says modifier 25 “should only be used on claims for evaluation and management (E/M) services.” Ch. 12, §30 also says modifier 59 “is not appropriate to use with weekly radiation therapy management codes (77427) or with evaluation and management services codes.” A line that breaks a rule like these can come back with CARC 4.

Common triggers for PR-4

1. Modifier 25 on a code that is not an E/M service. For example, 25 is added to a procedure line.
2. Modifier 59 on an E/M code. CMS says 59 does not belong there.
3. Conflicting modifiers on one line. The payer may add remark N519.
4. A modifier left off a code that needs one.
5. An old code or modifier. Consider a code that changed at the start of the year.
6. The group was set by the payer. The edit fired correctly, but the payer put the amount in PR.

Where PR-4 shows up in the 835

CLP*PCN40881*4*60.00*0.00*60.00*12*CLAIM552210~
SVC*HC:36415:25*60.00*0.00**1~
CAS*PR*4*60.00~
REF*0K*MOD-EDIT-25~

• Status code 4 means the claim was denied.
• The line paid $0.
• CAS*PR*4*60.00 put the full charge under patient responsibility.
• The optional REF line may name the payer policy behind the edit.
• This sample is illustrative only. Real remits vary.

How to fix PR-4: decision path

1. Confirm the CAS segment. Check the group (PR), the reason (4), and the amount. Save the remit.
2. Read the remark code and any policy REF line. N519 points to a modifier combination.
3. Check the code and modifier pair for the date of service against the payer’s modifier rules.
4. Check the documentation. Does it support the modifier on that line?
5. Correct the line. Remove the wrong modifier, fix the conflict, or add the one that is missing.
6. Resubmit as a corrected claim, or follow the payer’s rule for a rejected claim.
7. Ask the payer why the amount is in PR. A modifier edit is not a deductible or a copay.
8. Hold the patient bill until the payer confirms the patient share.

Medicare, commercial and Medicaid notes

Medicare. CMS says a provider may bill the patient for a PR adjustment and not for a CO adjustment. Since CMS lists CARC 4 with CO in its 2005 table, a PR group on this reason deserves a question to your contractor.

Commercial. Group code use varies by payer. Ask the payer which rule put the amount in PR and whether your contract lets you bill it to the patient.

Medicaid. State programs publish their own modifier lists and billing rules. Check the state provider manual before you bill the patient.

Worked example (illustrative)

A lab bills 36415 with modifier 25 for a blood draw. The remit shows CAS*PR*4*60.00.

Reading it: Modifier 25 is for E/M services under CMS Ch. 12, §30.6.6 B. It does not belong on a specimen collection code.

Check: The chart shows only the draw. No separate E/M service was documented.

Fix: The biller removes modifier 25 from the line and sends a corrected claim. The biller also calls the payer to ask why the original amount was placed under patient responsibility, and holds the patient statement until the payer answers.

Second scenario: The payer says the PR amount is a real deductible applied to the allowed amount. The biller then bills the patient only for that amount.

Prevention checklist

• [ ] Add claim edits for common modifier rules, such as 25 on non-E/M lines.
• [ ] Update CPT, HCPCS and modifier tables before each January.
• [ ] Hold patient statements on any PR line with reason 4.
• [ ] Track PR-4 by payer to spot wrong group code use.
• [ ] Train coders on modifier rules from CMS and the payer.
• [ ] Keep the CARC and RARC guide handy for staff training.

Related denial codes

• CO-4: the same reason under the contractual group.
• PR-1, PR-2 and PR-3: deductible, coinsurance and copay.
• CO-11: diagnosis inconsistent with the procedure.
• CO-16: claim lacks information or has a billing error.
• CARC and RARC guide.

Key takeaways

PR-4 is a modifier problem that the payer filed under patient responsibility. Fix the modifier and resubmit. Ask the payer why the group is PR, and hold the patient bill until it confirms the amount.

FAQ

Quick facts

Item	Value
X12 code	4
X12 start	01/01/1995
Last modified	03/01/2020
Official wording	The procedure code is inconsistent with the modifier used
Group on this page	PR
CMS 2005 group for CARC 4	CO
Common confusions	CO-4 (same reason, CO group), N519 (modifier combination)
Last reviewed	16 October 2026

Sources

• X12, Claim Adjustment Reason Codes (CARC 4, 11, 16). CARC 4 Start 01/01/1995; Last Modified 03/01/2020. Accessed 16 Oct 2026.
• X12, Remittance Advice Remark Codes (N519). Accessed 16 Oct 2026.
• CMS, Medicare Claims Processing Manual (IOM 100-04), Ch. 22, §60.1 Group Codes. Accessed 16 Oct 2026.
• CMS, Medicare Claims Processing Manual (IOM 100-04), Ch. 12, §30 and §30.6.6 B. Accessed 16 Oct 2026.
• CMS, Medicare Claims Processing Manual (IOM 100-04), Ch. 26, Item 24D. Accessed 16 Oct 2026.
• CMS, Transmittal 470 (4 Feb 2005). Accessed 16 Oct 2026.
• Medical Billing 101, CO-4 guide.

Code wording and Medicare rules on this page were checked on 16 October 2026 against X12 and CMS sources.

Last reviewed: 16 October 2026 · This page is educational and doesn’t replace payer-specific contracts or coding rules.