PTCB NDC, Lot Numbers and Expiration Dates study guide

What this topic actually asks of you

Domain 4 of the PTCE is Order Entry and Processing, and it carries 22.50% of the exam. Two of its knowledge areas are the paperwork printed on the box:

Lot numbers, expiration dates, and National Drug Code (NDC) numbers

That is KA 4.3, and

Procedures for identifying and returning dispensable, non-dispensable, and expired medications and supplies (e.g., credit return, return to stock, reverse distribution)

That is KA 4.4. Together they are the exam's only look at the three identifiers a package carries — and the one part of Domain 4 where a wrong answer is not an arithmetic slip but a legal one.

Every one of the three identifiers has an owner. That is the single idea this topic is built on. The NDC's first segment is assigned by the FDA; the other two by the labeling firm. The lot number is assigned by the manufacturer. The expiration date is set by the manufacturer from its own stability data — and the beyond-use date, the one that looks like the expiration date, is set by the pharmacist. A question that asks who decides this number is asking whether you know where the number came from, and a technician who mixes the last two up will dispense a repackaged product past the date it was actually good for.

The 11-digit rule is the one arithmetic fact. NDCs are printed in three different 10-digit layouts and billed in one 11-digit layout, so a technician has to be able to pad the right segment. A question can turn on it, a pharmacy's own system flags it, and getting the segment wrong is the difference between a paid claim and a rejection.

The rest of this topic is the counter work around expired stock: what may go back on the shelf, what may never be redispensed, and where the two legal regimes — the pharmacy's own returns procedure and the DEA's — meet.

Four facts every package carries

Read any stock bottle and you are reading four markings, each with a different author and a different job. Getting them straight is most of KA 4.3.

The NDC, segment by segment

The NDC's three segments

A National Drug Code is ten digits today, in three segments separated by hyphens:

• Labeler code — the first segment. It identifies the firm that manufactures, repackages or distributes the drug, and it is assigned by the FDA.
• Product code — the middle segment. It identifies the drug itself: the active ingredient, strength and dosage form. The firm assigns it.
• Package code — the last segment. It identifies the package size and type. A 30-count bottle and a 100-count bottle of the same tablets share the first two segments and differ in the third.

So the exam's version of the rule is: FDA assigns one segment, the firm assigns the other two. That is the fact to hold, because the intuitive guess — "the government assigns the whole number" — is wrong.

The package code is the one that catches people in practice. Two bottles that hold the same tablets are two NDCs — the same drug, the same strength, the same dosage form, and two identities. You bill the NDC of the bottle you actually counted from, and billing a package other than the one dispensed is a billing error an audit catches, even when the claim pays.

The three 10-digit configurations, and the 11-digit billing form

Ten digits split into three segments three ways, and all three are in use on real labels. Which segment is short is what tells you where the zero goes.

Read the table by its columns, not its rows. The billing form is always 5-4-2. What changes is which segment was written short on the label, and a short segment is padded back to its billing length by adding a leading zero — never a trailing one, and never to a segment that is already the right length.

• In a 4-4-2 NDC the labeler is short, so the zero goes in front of the labeler: 1234-5678-90 → 01234-5678-90.
• In a 5-3-2 NDC the product is short, so the zero goes in front of the product: 12345-678-90 → 12345-0678-90.
• In a 5-4-1 NDC the package is short, so the zero goes in front of the package: 12345-6789-0 → 12345-6789-00.

Three configurations, one rule, one destination format. FDA has published a final rule to move the NDC to a uniform twelve-digit format: published March 5, 2026 and taking effect on March 7, 2033, when FDA converts every existing NDC by adding leading zeros. Until then, labels carry ten digits and billing uses the eleven-digit 5-4-2 form — which is the form a question tests. FDA also says it will not object to ten-digit NDCs on labels from March 7, 2033 through March 6, 2036, so the changeover has a window rather than a cliff.

Converting a 10-digit NDC to the 11-digit form

The conversion is four steps and no arithmetic at all — it is counting:

1. Split the printed NDC into its three segments at the hyphens.
2. Count each segment against the target lengths 5, 4, 2.
3. Pad the one that is short with a leading zero. There is never more than one short segment, and never a segment that is too long.
4. Rejoin with hyphens — the result is always 5-4-2.

Work three of them, one per configuration:

• 1234-5678-90 is 4-4-2, so the labeler is one digit short → 0 + 1234 → 01234-5678-90.
• 12345-678-90 is 5-3-2, so the product is one digit short → 0 + 678 → 12345-0678-90.
• 12345-6789-0 is 5-4-1, so the package is one digit short → 0 + 0 → 12345-6789-00.

The trap the PTCE sets is padding the wrong segment. A 5-3-2 NDC padded at the labeler gives 012345-678-90 — eleven digits, but in a 6-3-2 layout that no billing system accepts. Counting each segment against 5-4-2 after the pad is what catches it.

Matching the NDC to the order and the claim

On the counter, the NDC is the thread that has to stay straight from the prescription to the adjudication:

• The NDC on the stock bottle must match the NDC on the label and on the claim. Same drug, same strength, same dosage form, same package size. The package code is part of the identity — that is why the pharmacy counts from the bottle it billed.
• The billing unit is how the payer counts the product: usually each (tablets, capsules, patches), sometimes mL or grams for a liquid or a cream. Quantity billed is stated in that unit, and it follows the dosage form — tablets count as each, a liquid or a cream as mL or grams — not the package code.
• "NDC not covered" means the plan does not cover that NDC. A covered alternative has to be found — another manufacturer or package the plan lists, a formulary alternative, or a prior authorization — and the technician's job is to read the rejection and work out which, not to assume a different NDC is covered.
• A product whose NDC changes — a new labeler, a repackager, a relabeled generic — is a new NDC even when the tablets are identical. Nothing about the drug's name guarantees the NDC.

Two dates that look alike, and are not

Expiration date and beyond-use date are not the same thing

Both are dates past which a product should not be used, and that is where the resemblance ends. The exam separates them by who assigned the date and what the container was.

Four rules that do the work:

• The expiration date belongs to the product in its original container, stored as labeled. A pharmacy dispenses from an opened, reclosed stock bottle up to that date. Once the pharmacy divides the product — repackaging tablets into unit-dose cards, drawing a liquid into a syringe, compounding a cream — the question is no longer what the manufacturer promised but what the pharmacist can support, and that answer is a BUD.
• A BUD is never later than the manufacturer's expiration date on the bulk container. The pharmacy's date can only shorten the projection, never extend it.
• USP sets the maximum BUD by the type of preparation — nonsterile preparations under USP <795>, sterile ones under USP <797> — and a pharmacy may only go past a default BUD if it has its own documented stability data for that preparation.
• The date is inclusive. A product marked EXP 06/2027 is usable through June 30, 2027 — when only a month and a year are printed, the product expires on the last day of that month, not the first.

There is a third clock worth knowing: the beyond-use date of an opened multi-dose vial. Once a multi-dose vial is opened (needle-punctured), it is dated and — per the CDC — discarded within 28 days, unless the manufacturer states another date for that opened vial; that date never runs past the product's own expiration date. A single-dose vial is a different case: it is for one patient, it does not get the 28-day period, and its leftover contents are never pooled. A question can set the expiration date, a compounded BUD, and this opened-vial date as three different choices.

Working a date question

Date questions have two shapes, and both are counting rather than calendar reasoning.

Shape one: a printed month and year. The whole month is inside the date, so the last usable day is the month's last day. EXP 06/2027 means usable through June 30, 2027 — the reading that stops at June 1 throws away nearly a month of good product.

Shape two: a BUD counted forward from a preparation date. Add the number of days to the date the preparation was made. The day of preparation is where the count starts; the BUD is the day the count lands on.

• Reconstituted July 5, 2026 with a 14-day BUD → July 19, 2026.
• A 30-day BUD on a preparation made August 20, 2026 → September 19, 2026 (11 days of August take the count to August 31, and 19 days of September finish it).
• A 60-day BUD on a preparation made February 10, 2026 → April 11, 2026. February has 28 days in 2026, so the count runs through the months in three legs: February 10 to February 28 is 18 days, that 28-day month leaves 31 days of March to reach 49, and 11 more days land on April 11.

Two habits prevent the errors a likely distractor turns on. Count in month-sized legs rather than trying to hold a long span in your head, and check whether the span crosses February — a 28-day month is where counting "60 days" as two calendar months gives April 10, one day short.

The barcode, and the DSCSA product identifier

Two different machine-readable codes sit on a drug package, and the exam expects them kept apart.

• The linear barcode (the FDA barcode rule, 21 CFR 201.25) encodes the NDC. It exists so the drug can be scanned at the point of dispensing and matched against the prescription — a second, machine check of the identity a human is also reading.
• The 2D data-matrix barcode (the DSCSA product identifier) encodes the product identifier, which is four things: the NDC, a serial number unique to that one package, the lot number, and the expiration date. The statute describes the product identifier as printed in both its human-readable and its machine-readable form on the package.

The NDC plus the serial number is the standardized numerical identifier (SNI) — the piece that makes one bottle distinguishable from every other bottle of the same NDC. The serial number is what lets one package be traced — from the manufacturer, through the wholesaler, to the pharmacy that dispensed it — without anyone relying on a lot number alone, which is shared by a whole batch.

Practically, the two codes answer different questions. The linear barcode answers what is this drug; the 2D product identifier answers which package is this, and when does it expire. Verifying a product identifier on a saleable return is a supply-chain duty the statute puts on the wholesale distributor, not on the dispensing pharmacy. The dispenser has its own duty: when it investigates suspect product, it must verify the product at the package level, the standardized numerical identifier (SNI) included (21 USC 360eee-1(d)(4)(A)(ii)) — a job a technician supports but the pharmacist owns.

Lot numbers: the number a recall is run on

A lot number (also called a batch number) is assigned by the manufacturer to a quantity of drug made in one run under uniform conditions. It carries no arithmetic and no meaning on its own — its value is entirely in what it lets someone do later.

It is the index of a recall. When a manufacturer finds a defect, the recall names the lot numbers affected. The pharmacy's job is to compare the recalled lot numbers against the stock in front of it, pull every match, and follow the recall notice's instructions — which may mean returning the stock, quarantining it, or contacting patients already dispensed. Without the lot number there is no way to tell the bad tablets from the good ones in the same cabinet.

Two consequences a question can turn on:

• Lot numbers are not interchangeable between products, and one product has many lots. A recall of one lot does not recall the drug.
• The lot number has to be recorded where it can be found. A repackaged product carries a new label, and the original manufacturer's lot and expiration — or the pharmacy's own tracking of them — must not be thrown away with the bulk bottle, because that is the only route back to a recall.

Dispensable or non-dispensable

When stock comes back to the counter, a technician has to answer one question before touching it: may this go back into the stock that gets dispensed to a patient? That is the whole of KA 4.4, and the vocabulary is two words.

Dispensable means the product may return to usable stock and be dispensed to another patient. Non-dispensable means it may not — and the word describes the product's status, not its condition.

Two things the table is telling you. The first is that "unopened" is not the test — a sealed patient return is still non-dispensable, because the pharmacy cannot see what happened to it. The second is that non-dispensable is not the same as destroyed: a non-dispensable product still has a correct destination, and the next sections are those destinations.

Expired stock: pull it, quarantine it, rotate FEFO

Expired stock is identified by date, pulled out of usable stock, and moved somewhere it cannot be dispensed from by accident.

• Rotate first-expired, first-out (FEFO). The stock that comes off the shelf first is the stock that expires soonest, not the stock that arrived soonest. FEFO is the dating version of FIFO, and it is the reason a well-kept shelf rarely has anything to pull.
• Date-check on receipt, then again on the shelf. A month- and year-dated product is checked as store policy defines — often within the last month it is usable — and never only after it.
• Pull and quarantine. Expired stock leaves usable shelf space and goes into a marked area or container kept for expired and unusable product. Stock that is still in the aisle is stock that gets dispensed by mistake.
• Controls are counted. A perpetual inventory is store policy or state law, not a federal requirement — what federal law requires is a biennial inventory of controlled substances (21 CFR 1304.11). It is what shows an expired controlled substance was removed rather than lost.
• A product that cannot be ordered is checked, not guessed. When supply is short, the FDA's Drug Shortages database (fda.gov/drugs/drug-shortages) is where a technician confirms whether a national shortage exists and how long it is expected to run.

Returns: credit, return to stock, reverse distribution

KA 4.4 names three procedures, and they differ by where the product is going.

Return to stock — an unclaimed prescription. The product is the pharmacy's own, already packaged and labeled, and the patient never collected it.

1. Confirm nothing happened to it: original container, sealed, correctly stored, not expired, not a compounded preparation.
2. Return it to usable stock, with its lot number and expiration date intact on the pharmacy's label — the label is the only record of which lot went back on the shelf.
3. Reverse the insurance claim. A claim that is not reversed bills the payer for a drug no patient received. This step is the one candidates forget, and it is the reason the procedure is on the outline.
4. Document the return and the reversal. How long a prescription may sit before it is returned — and whether a given product may be returned at all — is state law and store policy, so the honest answer to "how many days?" is it depends on the state and the pharmacy.

Credit return — product going back up the supply chain. Unopened, unexpired stock may be returned to the wholesaler for credit, under the wholesaler's own return policy. The wholesaler decides whether to credit it. Controlled substances are their own case: federal rules let a pharmacy return a controlled substance to the person or supplier it obtained it from, or to the manufacturer (21 CFR 1307.12), or hand it to a reverse distributor (21 CFR 1317.05) — so a controlled return goes back up the chain under those rules, not for open credit.

Reverse distribution — the destination for everything that is not dispensable. A reverse distributor is a firm registered to receive expired, damaged, unusable and recalled product — controlled substances included — and to take it the rest of the way: the credit, or the destruction, and the paperwork either way. It is the answer to where does the expired stock go, and it is a different word from the wholesaler on the exam.

The legal scaffolding around it:

• Controlled substances that leave the pharmacy are recorded (21 CFR 1307.12). A pharmacy may return them to its supplier or the manufacturer (21 CFR 1307.12); sending them to a reverse distributor is a separate route under 21 CFR 1317.05. A Schedule I or II return uses a DEA order form (Form 222 or CSOS, 21 CFR Part 1305) — the same form used to order them — while a Schedule III, IV or V return is documented with a written record rather than that form.
• Disposal and take-back live in 21 CFR Part 1317. To take back controlled substances from the public a pharmacy must register with DEA as an authorized collector (Part 1317); collection then runs through an on-site receptacle that is securely fastened and stays inside, or mail-back envelopes. The registration is the step that authorizes it.
• Destruction must be non-retrievable. The product has to be rendered unusable so it cannot return to circulation; that standard is what separates disposal from putting a bottle in the trash.
• Patient-returned medication is never restocked — that is the standard of practice and state board rule (near-universal, with narrow exceptions: institutional unit-dose and drug-repository programs). Federally only controlled substances are restricted, and those go through DEA take-back. Take-back is where it goes, not the shelf.

Why three words instead of one: return to stock keeps the product in the pharmacy, credit return sends it back to the seller, and reverse distribution sends it out of the supply chain for good. A question that names one of the three is asking which direction the product travels.

The pairs that get mixed up

Every wrong answer in this topic is a substitution of one word for the one beside it. These are the pairs to separate deliberately.

The last thing to fix is the reflex that answers who assigns it with "the FDA." The FDA assigns one of the NDC's three segments and no part of the lot number or the dates. The firm, the manufacturer and the pharmacist own the rest, and a question that names one of them is testing whether the ownership was learned or assumed.

How to practice this

• Read the free NDC, lot and expiration practice set and name the job before you choose: identify it, date it, or return it. Naming the job is what stops an expiration date being read as a BUD.
• Convert three NDCs from memory — one 4-4-2, one 5-3-2 and one 5-4-1 — then count the digits either side of each hyphen. The three worked conversions in this guide are the whole method.
• Write the four ownership facts on one line: FDA → labeler; firm → product and package; manufacturer → lot and expiration; pharmacist → BUD. Most wrong answers here are an ownership swapped.
• Drill the pairs above as flashcards, front to back and then back to front. Every one of them is a substitution a question can offer as a distractor.
• Re-attempt what you missed a day later rather than immediately, and work the administration equipment and supplies guide if the storage and date-dating side of Domain 4 is where you lose points, or the order interpretation and sig guide if reading a prescription is the part that goes past you.

Where to go next

• Next topic — the PTCB hub — all eleven topics, in course order.
• The exam itself — the passing score, how many questions, and what makes the PTCB exam hard.

This topic sits inside Domain 4 — Order Entry and Processing, 22.50% of the exam — the outline's own weight, and PTCB publishes no per-knowledge-area split.

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