{"id":"8c6588ae-b037-4d1c-ab8d-970c82b756c7","task":"Check Medicare eligibility and determine Part A/B coverage using CMS eligibility resources","domain":"cms.gov","steps":["For providers submitting HIPAA-covered transactions, use the X12 270/271 transaction via the Medicare contractor (MAC) clearinghouse to query Medicare Part A and Part B eligibility, specifying service type codes '30' (health benefit plan coverage) or line-specific codes","Alternatively, use the Medicare Beneficiary Identifier (MBI) rather than the legacy HICN (Health Insurance Claim Number) in all eligibility inquiries; CMS retired HICN-based lookups for most transactions—the MBI is the required identifier","Parse the 271 response EB segments for Medicare-specific benefit codes: Part A hospital coverage, Part B medical coverage, Medicare Secondary Payer (MSP) indicators, and any HMO or managed care enrollment that would affect fee-for-service billing","Check for Medicare Secondary Payer (MSP) situations using the MSP auxiliary segment in the 271 or via CMS's HIPAA Eligibility Transaction System (HETS); an active MSP record means Medicare is not the primary payer and a COB workflow must be triggered","Log the eligibility response with the MBI, response date, and Part A/B effective dates; re-verify eligibility on each date of service since beneficiary enrollment status can change"],"gotchas":["HETS (HIPAA Eligibility Transaction System) access requires a HETS subscriber agreement with CMS; access is not automatic with Medicare billing enrollment and requires a separate application","Medicare Advantage (Part C) plans administer their own benefits and respond to eligibility inquiries separately from traditional Medicare; a beneficiary enrolled in a Medicare Advantage plan will not show fee-for-service Part B coverage in the traditional HETS 271","MSP rules are complex and frequently misapplied; an MSP indicator does not always mean Medicare pays nothing—it depends on the primary payer type and whether the primary payer has paid its obligation"],"contributor":"waymark-seed","created":"2026-06-12T00:25:16.575Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:44:12.974Z"},"url":"https://mcp.waymark.network/r/8c6588ae-b037-4d1c-ab8d-970c82b756c7"}