NDC numbers and beyond-use dates for the PTCB exam

The NDC number's 5-4-2 structure and the 11-digit billing conversion, what a lot number is for, and the distinction the exam actually tests: an expiration date is not a beyond-use date.

NDC Format and Structure

Where the NDC Comes From, and What the Pharmacy Uses It For

Drug manufacturers register listed products with the FDA through the Drug Registration and Listing System (DRLS), and that registration supports assignment of the National Drug Code. Pharmacies rely on the NDC for product verification during dispensing, for claim submission through the NCPDP billing format, and for recall response when a manufacturer or the FDA publishes an affected-lot list.

The Three Segments — Labeler, Product, Package

The printed NDC is a 10-digit identifier, and manufacturers break it into one of three common groupings: 4-4-2, 5-3-2, or 5-4-1. The number of digits in each segment tells you the layout, which in turn tells you which segment needs a leading zero for billing. The first segment is the labeler (manufacturer) code and is assigned by the FDA. The middle segment is the product code, assigned by the manufacturer, and captures the formulation, dosage form, and strength. The final segment is the package code, also assigned by the manufacturer, and captures package type and package size.

Callout — The NDC is three pieces of information, not one. Labeler (who made it), product (what formulation and strength), package (what container size). Match all three or you have matched nothing.

11-Digit NDC Billing Format (5-4-2) — Zero-Padding Rules

Insurance claims under the NCPDP format (a HIPAA standard) require an 11-digit NDC in the 5-4-2 layout. You convert a 10-digit NDC to 11 digits by adding a leading zero to whichever segment is short. You never modify the other two segments.

Worked example 1 (4-4-2 to 5-4-2): 10-digit 0002-7597-01 — the labeler segment has four digits, so the zero goes there. Result: 00002-7597-01.

Worked example 2 (5-3-2 to 5-4-2): 10-digit 50242-040-62 — the product segment has three digits, so the zero goes there. Result: 50242-0040-62.

Worked example 3 (5-4-1 to 5-4-2): 10-digit 60505-2574-1 — the package segment has one digit, so the zero goes there. Result: 60505-2574-01.

Callout — Safety rule on the billing NDC. The 11-digit NDC is added to the claim only. The printed 10-digit NDC on the physical bottle does not change. Putting the leading zero in the wrong segment bills a different labeled product — that is a dispensing and reimbursement problem in one move.

NDC Numbers in Practice

In daily workflow, the NDC is how staff distinguish one specific labeled product configuration from every other one. Matching the NDC means matching more than the drug name — strength, dosage form, and package size have to line up with whatever is being selected and billed. That precision is what makes the NDC useful for dispensing accuracy, claim submission, automated repackaging calibration, and recall action. Two bottles with the same drug name but different NDCs are not the same product from an inventory or billing standpoint.

Lot Numbers

A lot number (also called a control number) is assigned by the manufacturer to identify a specific production batch. Every bottle, vial, carton, or unit-dose blister that came off that run shares the same lot number. The lot number is the hinge point for three distinct workflows:

Here's where people miss it. On the PTCE, a recall question that hands you a lot number is almost never asking you to explain DSCSA serialization — it is asking you to confirm that you check your shelves, your automation canisters, and any will-call bags against the recall list. The lot number is the search key.

Expiration Dates and Beyond-Use Dates

An expiration date is the last date that an unopened commercial product is expected to remain within its quality specifications when stored as directed. Manufacturers assign expiration dating from formal stability studies, not from the USP BUD rules used in the pharmacy. Past the expiration date, the product cannot be legally dispensed.

When a label prints only a month and year (for example, "EXP 08/31"), treat the product as expiring on the last calendar day of that month. On the exam that means August 31, 2031 — not August 1.

Expiration Date vs. Beyond-Use Date

Expiration dates and beyond-use dates are not the same thing. Manufactured pharmaceuticals have expiration dates. Compounded or repackaged medications are assigned a BUD by the pharmacy staff who prepared them. BUDs take contamination risk and storage conditions into account, and a compounded or repackaged item can never receive a BUD that extends past the earliest remaining expiration date of any ingredient used in it.

Repackaged-Drug BUD — the 25 Percent Rule

For nonsterile repackaging into unit-dose containers, labeling is the responsibility of the dispenser and has to consider the drug's characteristics, the container's properties, and storage conditions. Current FDA guidance generally limits the assigned BUD to the earliest of three candidates:

1. Six months from the date of repackaging.
2. Twenty-five percent of the time remaining between the repackaging date and the manufacturer's expiration date.
3. The manufacturer's expiration date itself.

Worked example (25 percent rule): You are repackaging a bulk bottle of tablets on January 1, 2026. The manufacturer expiration date on the bottle is January 1, 2027, meaning 12 months of remaining shelf life.

• Candidate 1: six months from repackaging = July 1, 2026.
• Candidate 2: 25 percent of 12 months = 3 months = April 1, 2026.
• Candidate 3: manufacturer expiration = January 1, 2027.
• Take the earliest: the assigned BUD is April 1, 2026.

Callout — The 25 percent rule is an "earliest of" rule, not an "average of" rule. Compute all three candidates. Pick the one that comes first on the calendar. That is your BUD.

USP <795> Nonsterile Default BUDs

USP <797> Sterile CSP BUDs

Either default yields to the earliest remaining ingredient expiration — that is the hard ceiling you never cross.

Receiving and FIFO

During receiving, staff confirm that the product's dating meets the site's minimum shelf-life policy (often six months). Incoming stock is compared against existing inventory, and short-dated items get rotated forward. Anything already expired has to leave active stock and move to the appropriate quarantine or returns area.

Stock rotation means placing the soonest-to-expire product where it will be pulled first. Newer, longer-dated product is moved behind older stock. Many sites call this FIFO, though the practical goal is "earliest expiration out first."

Mnemonic: "First In, First Out (FIFO)" — oldest stock on the front; newest behind. Reduces expired-dispense risk. See the Mnemonic Library cheat sheet Section 10 for the recall and supply-chain anchor cluster.

Common Traps

• Do not confuse the NDC, lot, and expiration fields — they do not appear in the same order or typeface on every manufacturer's package.
• Do not read a routine label question as a DSCSA tracing question; 4.3 is label reading, 2.6 is chain of custody.
• Do not treat "expiration" and "BUD" as synonyms. Manufactured stock has an expiration date. Compounded or repackaged product gets a BUD.
• When padding an NDC, never move the zero to a segment that is not actually short.
• An "08/31" expiration does not mean August 1; it means the last day of August.

Quick Review Checklist

NDC structure: - Manufacturer NDCs are 10 digits, printed as 4-4-2, 5-3-2, or 5-4-1. - First segment: labeler/manufacturer (FDA-assigned). - Middle segment: product (formulation, dosage form, strength). - Final segment: package type and size. - Used for dispensing, ordering, billing, automation, and recalls.

NDC 11-digit billing padding (5-4-2): - 4-4-2 → pad labeler (first) with a leading 0. - 5-3-2 → pad product (middle) with a leading 0. - 5-4-1 → pad package (last) with a leading 0. - Putting the zero in the wrong segment bills a different product (safety and reimbursement problem).

DSCSA product identifier (four elements, one 2D barcode): - NDC, serial number, lot number, expiration date.

USP <795> nonsterile default BUDs: - Non-aqueous oral liquids: up to 90 days; other non-aqueous (capsules, tablets, suppositories): up to 180 days. - Aqueous non-preserved: up to 14 days refrigerated. - Aqueous preserved: up to 35 days at controlled room temperature or refrigerated.

USP <797> sterile CSP BUDs: - Category 1: up to 12 hr RT, up to 24 hr fridge. - Category 2 (default, sterile starting components): 4 days RT / 10 days refrigerated / 45 days frozen. Longer BUDs only with passed sterility testing — aseptically processed + tested = 30 / 45 / 60 days; terminally sterilized + tested = 45 / 60 / 90 days (RT / refrigerated / frozen). - Category 3 — aseptically processed: 60 days RT / 90 days refrigerated / 120 days frozen. Terminally sterilized: 90 days RT / 120 days refrigerated / 180 days frozen. Both require passed sterility and endotoxin testing plus enhanced garbing and monitoring.

Repackaged-drug BUD — earliest of: - 6 months from repackaging. - 25 percent of remaining time to manufacturer expiration. - Manufacturer expiration date.

Lot numbers: - Also called control numbers. - Assigned by the manufacturer to a specific batch. - Three uses: tracking/tracing, recalls, quality control.

Expiration dates: - The last date a drug product may be used. - Month/year only = last day of that month. - Checked on receiving, compared to stock on hand, rotated FIFO. - Derived from manufacturer stability studies, not USP BUD rules.

Outpatient label core items: - Patient name, fill date, prescriber name, Rx number. - Drug name, strength (and manufacturer when generic). - Quantity dispensed, directions in plain language, pharmacy name and address. - Refill information, cautionary statements when applicable.

Repackaged label (7 items): - Generic name (and brand when appropriate), dosage form/strength. - Amount in package, extra directions. - Expiration date, lot/control number, barcode.

Tall-man lettering recognizers: - hydrOXYzine / hydrALAZINE, predniSONE / prednisoLONE, DOPamine / DOBUTamine, vinBLAStine / vinCRIStine.

"Rx Only" legend: - FDAMA 1997 replaced the older "Caution" legend with the simpler "Rx Only."

Related

All Order Entry and Processing guides · What is on the PTCE and how it is weighted · The Federal Requirements domain