How a pharmacy claim is processed

A pharmacy claim is usually settled before the customer reaches the register. The standards body that writes the format, the National Council for Prescription Drug Programs (NCPDP), says on its history page¹ that its Telecommunication Standard lets the pharmacy learn "within seconds" whether a patient is eligible, whether the drug is covered and what the copay is. The pharmacy, it adds, "knows almost instantly how much it will be paid."

That speed rests on a federal mandate. Since January 1, 2012, every retail pharmacy claim sent electronically by a HIPAA-covered pharmacy or health plan has had to use NCPDP's Version D.0, according to the CMS table of adopted HIPAA standards⁴. In December 2024 the Department of Health and Human Services adopted its replacement, Version F6, in a final rule⁸ that, after a later date correction, takes full effect on April 14, 2028.

Most people see only the outcome, a price or a message that the plan "won't cover it." This piece follows a claim from the numbers on an insurance card to the codes that come back on a rejection, and what the next version changes.

The federal rule behind every claim

Congress told HHS, in the Health Insurance Portability and Accountability Act of 1996, to pick national formats for routine electronic health transactions. For most of health care the chosen format is the X12 family of standards. Retail pharmacy is the exception. The CMS standards page⁴ lists NCPDP Version D.0 for "pharmacy and supplier transactions" and NCPDP Version 3.0 for Medicaid subrogation, the process states use to recover payments from other insurers.

The lineage shows in the regulation itself, 45 CFR 162.1102⁵. NCPDP Version 5.1 was the required format from October 16, 2003, through March 16, 2009. HHS adopted Version D.0 in a January 16, 2009 rule⁷, with both versions allowed until the end of 2011. A companion rule on code sets, 45 CFR 162.1002⁶, names National Drug Codes as the standard way retail pharmacies identify the drug being dispensed, which is why the 11-digit NDC on the stock bottle is the key piece of data on every claim.

NCPDP is an accredited standards developer whose members include pharmacies, health plans, claims processors, drug makers and federal agencies, according to its description of itself².

What the card numbers do

A prescription insurance card usually carries four routing items, often labeled RxBIN, RxPCN, a group number and an ID. The BIN tells the pharmacy's software where to send the claim. NCPDP's guidance on processor IDs³ describes its Processor ID (BIN) as "a six-digit number that health plans can use to process electronic pharmacy claims," and notes that the banking-style Issuer Identifier Number moved from six digits to eight in January 2017. The PCN (processor control number) and group number then sort the claim to the right benefit plan, and the cardholder ID points to the person.

Medicare Part D formalized the system. Under 42 CFR 423.120(c)¹¹, beginning January 1, 2012, every Part D sponsor must assign and use a unique Part D BIN or RxBIN and PCN combination for its Medicare business, plus a Part D cardholder ID for each enrollee, so pharmacies can tell a Medicare claim from a commercial one at the same processor.

Between the pharmacy and the payer sits a telecommunication switch. In the 2024 rule, HHS said switches "validate the format of pharmacy transactions prior to transmission to the payer and then check the payer response," and that it had identified three switches in the market. The payer on the other end is often a claims processor working for a plan, a role our explainer on pharmacy benefit managers covers.

What travels in the claim and the response

State Medicaid "payer sheets" listing required fields are the clearest public view of a D.0 claim. California's Medi-Cal Rx payer specification¹², version 8.0 dated August 21, 2026, accepts transaction codes B1 (claim billing), B2 (claim reversal), B3 (claim rebill), E1 (eligibility verification) and P2 through P4 for prior authorization. It publishes its own BIN, 022659, and PCN, 6334225. A selection of fields from that document:

How plans set the ingredient cost and fee they actually pay is covered in how pharmacies get paid and how dispensing fees work. The cash-price field is explained in our piece on usual and customary prices.

How to read a rejected claim

When the status comes back R, the reject code says why. The codes come from NCPDP's external code list. California's Appendix D of NCPDP reject codes¹³, dated April 1, 2026, lists the ones it returns, including these common ones:

Many rejects are fixed at the counter with a corrected birth date, a new card or a second insurer billed in the right order. Codes 75 and MR usually start a longer process involving the prescriber. Our explainers on prior authorization and step therapy, early refills and formulary and tiering exceptions cover those paths. Questions about whether a different product or quantity would go through belong with the pharmacist, the prescriber and the plan.

Rules for a Medicare claim that won't go through

CMS's appeals guidance¹⁴, updated July 6, 2026, says a pharmacist explaining that a drug is off formulary or needs prior authorization is not itself a coverage decision. Plans must instead arrange for network pharmacies to hand the enrollee a standardized notice, Form CMS-10147, "Medicare Drug Coverage and Your Rights"¹⁵, when a prescription cannot be filled under Part D and the problem cannot be resolved at the point of sale. A designated NCPDP response code tells the pharmacy to provide it. The code is not sent for some rejections, including a claim missing data and a "refill too soon" edit, the guidance says. Mail-order pharmacies have 72 hours to deliver the notice.

That notice explains how to ask the plan for a coverage determination. According to the CMS coverage determination page¹⁶, the plan must decide within 72 hours on a standard request or 24 hours on an expedited one, and for exceptions the clock starts when the prescriber's supporting statement arrives. People who have just switched plans get a cushion. Under 42 CFR 423.120(b)(3)¹¹, a Part D plan must provide a one-time temporary supply of at least a month of a non-formulary drug, or one that needs prior authorization, during the first 90 days in a new plan, and must send written notice within three business days.

Medicaid has its own floor. Section 1927 of the Social Security Act, at 42 U.S.C. 1396r-8(d)(5)¹⁷, allows a state prior authorization program only if it answers requests within 24 hours and allows at least a 72-hour supply in an emergency. Our guide to Medicaid preferred drug lists covers how states use that power, and how to appeal a drug coverage denial covers what comes after a denial.

What changes with Version F6

The December 2024 rule⁸ gave several reasons for replacing D.0, whose implementation guide is dated August 2007. Plan benefit details that D.0 sends as free text, such as the next date a refill will pay, prior authorization dates and minimum or maximum quantities, days' supply and dollar amounts, move to discrete data fields in F6. HHS said this "will enhance patient safety processes because there will be less room for interpretation." F6 also adds an eight-digit identifier field to the claim header, which the rule called the first change to that section of the standard since Version 5.1 was adopted in 2002, and it widens financial fields that topped out at $999,999.99, a limit one benefit manager told the National Committee on Vital and Health Statistics was the biggest issue for very expensive drugs.

Those dates moved after publication. A February 2025 rule delayed the effective date to April 14, 2025, and an August 2025 correction⁹ spelled out the new schedule. Either D.0 or F6 may be used during an eight-month transition starting August 14, 2027, and F6 alone is required from April 14, 2028.

A separate proposal could change what happens after a code 75. In an April 14, 2026 proposed rule¹⁰, CMS proposed requiring Medicare Advantage plans, state Medicaid and CHIP programs, their managed care plans and insurers on the federal marketplace to support electronic prior authorization for all drugs, through NCPDP standards and an application programming interface, beginning October 1, 2027. Comments closed June 15, 2026. As of early November 2026, no final rule had been published in the Federal Register.