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S00.542A Billable Code FY2027 Status: Active

S00.542A: External constriction of oral cavity, initial encounter

External constriction of oral cavity, initial encounter

Effective Date: 2026-10-01
Dataset: ICD-10-CM FY2027
Source: Centers for Disease Control and Prevention (CDC)
Last Verified: 2026-10-01
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Quick Clinical & Billing Summary

What is ICD-10-CM code S00.542A? S00.542A represents External constriction of oral cavity, initial encounter. Under official CDC guidelines, this code is billable and specific for claim submission.

Current release: FY2027 (Effective October 1, 2026). Sourced directly from CDC NCHS files.

Code Hierarchy & Classification

Chapter 19: Injury, poisoning and certain other consequences of external causes
⌊ Category S00: Superficial injury of head
⌊ S00.542A: External constriction of oral cavity, initial encounter (Current Code)

Clinical Guidance & Documentation Standards

Clinical documentation should substantiate the medical necessity of this diagnosis, including laterality, anatomical site specificity, and clinical severity.

7th Character Episode of Care Builder

Chapter 19 Requirement

ICD-10-CM coding guidelines mandate assigning an appropriate 7th character for traumatic injuries, fractures, and external causes to denote the episode of care:

A Initial Encounter
Patient receiving active clinical treatment (surgical evaluation, emergency care, initial casting).
D Subsequent Encounter
Patient receiving routine care during healing phase (cast change, medication adjustment, follow-up).
S Sequela (Late Effect)
Complications or conditions arising as a direct late consequence of the healed injury.
Placeholder X Rule: If the diagnosis code has fewer than 6 characters, you must append placeholder 'X' characters to maintain the 7th character position. Use 7th Character Builder Tool →

Associated Procedures & Medicare RVU Reimbursement

Open RVU Calculator →

Typical outpatient and office evaluation procedures frequently billed alongside diagnosis S00.542A:

CPT/HCPCS Description Work RVU Non-Facility Fee Facility Fee
99213 Office/outpatient visit, established patient, 20-29 minutes (Low MDM) 1.30 $91.69 $66.79
99214 Office/outpatient visit, established patient, 30-39 minutes (Moderate MDM) 1.92 $133.61 $100.21
96372 Therapeutic, prophylactic, or diagnostic injection (subcutaneous/intramuscular) 0.17 $18.34 $12.44
Based on official CMS 2026 Physician Fee Schedule conversion factor ($32.7476). Payments vary by locality GPCI.

CPT Modifier & Billing Rules

Modifier 25 Significant E/M

Append when a significant, separately identifiable evaluation and management service is provided on the same calendar day as a minor surgical procedure or injection.

Modifier 59 Distinct Service

Identifies procedures or services not normally reported together but distinct under the clinical circumstances. Use CMS X-modifiers (XE, XS, XP, XU) where required by Medicare.

Check NCCI Procedure to Procedure (PTP) unbundling rules in NCCI Checker →

Frequently Asked Questions about S00.542A

Is S00.542A a billable ICD-10 code?

Yes, S00.542A is a valid, billable and specific ICD-10-CM code. It can be reported as a primary or secondary diagnosis on medical claims.

What is the ICD-10 code for External constriction of oral cavity, initial encounter?

The primary ICD-10-CM code for External constriction of oral cavity, initial encounter is S00.542A.

What is the effective date of the current S00.542A code?

The code is active for fiscal year FY2027, effective starting 2026-10-01.

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Official Provenance: Sourced from CDC / NCHS FY2027 ICD-10-CM files. Report a Data Error
Verified: 2026-10-01