Medicare BIN, PCN & Group ID → Contract Crosswalk

What Are BIN, PCN, and Group ID?

These are the routing fields of a pharmacy claim, defined in the NCPDP Telecommunication Standard that every US pharmacy uses to submit prescriptions electronically. Together with the cardholder ID they are often called the 4Rx fields, and they are printed on the member’s ID card as RxBIN, RxPCN, and RxGrp. Each one narrows where the claim goes. None of them is the Medicare plan.

A contract ID is a letter and four digits (H for Medicare Advantage and cost plans, S for standalone PDPs, R for regional PPOs, E for employer direct contracts). Each contract offers one or more PBPs, numbered 001, 002, and so on. Contract, PBP, and plan year together identify one Medicare plan.

What the Crosswalk Does

The crosswalk is keyed at the grain CMS regulates, which is contract × PBP × plan year. It answers two questions that run in opposite directions:

claim  BIN 610011  PCN CTRXMEDD                    plan year 2026
   │
   │  reverse lookup on BIN + PCN
   ▼
257 candidate plans across 54 contracts
   │
   │  add RxGroup BCBSMAN
   ▼
1 plan    S5584-801    PBM: OptumRx

That narrowing, from 257 plans to one, is the whole argument for RxGroup. It is also why a crosswalk built only from what CMS publishes stops at the second box.

What CMS Publishes, and What It Leaves Out

CMS does publish Medicare BIN and PCN assignments. The Part D Information for Pharmaceutical Manufacturers page carries a contract/PBP-to-BIN/PCN file for the current year and a historical archive back to 2015. It is authoritative, and it is the spine of any serious crosswalk. It is also deliberately narrow.

If you only need the BIN and PCN for a known plan, the CMS file is the right answer and this page is context. The crosswalk becomes real work once you start from the claim and need the plan, the PBM, or the group, which describes most analytical uses.

Why the Crosswalk Is Valuable

Pharmacy claims, switch transactions, and prescription datasets all carry routing codes and none carry a Medicare contract. Whatever you want to learn about Medicare from claims data passes through this mapping, and the crosswalk’s precision caps how precise the answer can be.

One BIN/PCN Pair, Hundreds of Plans

In plan year 2026, 8,181 Part D plans route through just 191 BIN/PCN pairs. Only 554 plans (under 7%) sit on a pair used by a single contract. The rest share, and the largest pairs are shared at a scale that makes a BIN/PCN-only lookup close to meaningless:

Real rows, plan year 2026. Plans = distinct contract/PBPs routed on the pair.

A claim on 022188 / PSTMEDD could belong to any of 145 contracts. A claim on 610097 / 9999 could belong to any of 1,242 plans. Neither result tells you the plan. The first does not even give you the sponsor.

Why This Crosswalk Is So Hard to Build

Loading the CMS file takes an afternoon. Everything that makes the crosswalk useful beyond that file (the group, the PBM, and continuity across years) has to be assembled from sources that were never meant to be joined. Each of the following is a separate way to produce a mapping that looks right and is not.

Where the Evidence Lives

None of the sources beyond the CMS file are secret. Sponsors and PBMs publish them so pharmacies can bill claims and members can read their benefits. The difficulty is that they are spread across dozens of websites, each in its own format, and the routing values make up a tiny fraction of the pages they appear on. This is the evidence base behind the TwinFyRx crosswalk to date:

“Yielded a value” means the document produced at least one candidate BIN, PCN, or group. A candidate is not the same as an accepted value.

The yield column tells the story. The most plan-specific document a sponsor publishes, the Evidence of Coverage, is close to useless for routing, while the most useful one, the payer sheet, says nothing about which CMS contract it describes. Every candidate value then has to be tied to a plan, checked against the CMS pair for that plan and year, and either kept with its source or thrown away. That work is repeated every plan year, because sponsors republish these documents annually and routing changes underneath them.

How TwinFyRx Builds It

The build is evidence-first. The CMS file is the authoritative spine. Everything added on top of it is observed in public plan and pharmacy-facing documents, checked against that spine, and carried with its provenance. Four principles govern it:

Querying the Crosswalk

SELECT
    r.contract_id,
    r.pbp_id,
    r.rxgroup,
    r.pbm_name
FROM plan_routing r
WHERE r.plan_year = 2026
  AND r.bin       = '610011'
  AND r.pcn       = 'CTRXMEDD'
  AND r.rxgroup   = 'BCBSMAN';   -- drop this line to see all 257 candidates

SELECT
    r.bin, r.pcn, r.rxgroup,
    r.m3p_bin, r.m3p_pcn,
    i.pbm_name,
    i.confidence_label
FROM plan_routing  r
JOIN pbm_inference i USING (contract_id, pbp_id, plan_year)
WHERE r.contract_id = 'S5584'
  AND r.pbp_id      = '801'
  AND r.plan_year   = 2026;

SELECT
    bin,
    pcn,
    COUNT(DISTINCT contract_id)                 AS contracts,
    COUNT(DISTINCT contract_id || '-' || pbp_id) AS plan_count
FROM plan_routing
WHERE plan_year = 2026
GROUP BY bin, pcn
ORDER BY plan_count DESC;

API endpoints

Full request and response shapes are in the API reference. Table and column definitions for plan_routing, pbm_inference, and pbm_market_snapshot are on the schema reference.