Sources
Primary sources
Every code meaning and appeal framework on EOBDecode traces to one of the primary sources below. Last reviewed June 16, 2026.
Federal
Code lists, guidance & regulations
| Source | What it covers | Link |
|---|---|---|
| X12 — Claim Adjustment Reason Codes (CARC) | Authoritative published CARC list. | Open |
| X12 — Remittance Advice Remark Codes (RARC) | Authoritative published RARC list. | Open |
| CMS — Medicare Coverage Database | Local/National Coverage Determinations referenced by some RARCs. | Open |
| CMS — Medicare appeals & grievances | Medicare appeal levels and timelines. | Open |
| 29 CFR §2560.503-1 — ERISA claims procedure | Internal-appeal framework for ERISA group plans. | Open |
| 45 CFR §147.136 — ACA internal & external review | Internal claims/appeals + external review for ACA plans. | Open |
| 42 CFR Part 422, Subpart M — Medicare Advantage appeals | Medicare Advantage reconsideration and appeal levels. | Open |
| 42 CFR Part 431, Subpart E — Medicaid fair hearings | Federal floor for Medicaid fair-hearing rights. | Open |
| U.S. Department of Labor — benefit-claims guidance | Plain-language summary of ERISA appeal timeframes. | Open |
| HealthCare.gov — appealing an insurance decision | Consumer-facing internal/external appeal overview. | Open |
State
State external-review portals
Every state and DC operates an external-review process for fully-insured and individual-market plans, most following the NAIC Uniform Health Carrier External Review Model Act. Find your state's process at the NAIC consumer portal:
Per-state Department of Insurance URLs are maintained internally and refreshed annually. The appeal-letter generator points fully-insured and individual-market users to their specific state process.
Cross-check only
Secondary references
These are used only to sanity-check our plain-English layer — never as the load-bearing citation for a code meaning.
- Counterforce Health — common denial-code summaries
- Sprypt — CARC/RARC reference guide
- Provider revenue-cycle vendor explainers (BillingFreedom, MedCareMSO, Conifer)