Biennial Inventory Requirements for Veterinary Controlled Substances (2026)

A biennial inventory is the complete physical count of every controlled substance a veterinary practice holds, taken at least once every two years and signed and dated as a permanent record. It is a separate, freestanding requirement under 21 CFR 1304.11 — distinct from your day-to-day controlled substance log — and a missing or incomplete inventory is one of the most common findings in a DEA inspection.

This guide explains what the inventory is, how it differs from the initial inventory, how to count and record it correctly, and how it relates to your running log. A missed biennial inventory cannot be fixed retroactively — so the requirement is worth getting exactly right.

What the biennial inventory is

The biennial inventory is a point-in-time snapshot of all controlled substances in the practice’s possession on a single date. Under 21 CFR 1304.11, every DEA registrant must take a new inventory of all stocks of controlled substances on hand at least every two years.

It is not a running tally and not a process you do gradually. It is a discrete event: on one day, you count everything, write it down, and sign it. That signed document becomes a permanent record the practice keeps and can produce for the DEA.

“Biennial” means every two years — but it is a maximum interval, not a fixed date. The inventory may be taken on any date so long as it is within two years of the previous one. Many practices choose a fixed annual date (often January 1, or the practice anniversary) so the count is never overdue. Counting more often than the law requires is allowed and is good practice.

Initial inventory vs. biennial inventory

There are two distinct inventory obligations, and practices often confuse them.

The initial inventory is taken once, when the practice first engages in handling controlled substances — typically when a new DEA registration becomes active. It is the baseline. If the practice has no controlled substances on hand on that date, the initial inventory still must be taken and recorded — as a documented zero count.

The biennial inventory is the recurring count taken at least every two years thereafter. It is, in effect, the initial inventory repeated on a cycle.

One more case bridges the two: when a substance is newly added to a controlled-substance schedule, every registrant who already possesses that substance must take an inventory of it on the effective date of the scheduling. After that, it folds into the regular biennial count.

So the sequence is: initial inventory at startup → biennial inventory at least every two years → a special inventory of any newly scheduled drug you happen to hold.

How to count: opening or close of business

The inventory must be taken at a clean cut-off. Under 21 CFR 1304.11, the inventory may be taken either as of the opening of business or as of the close of business on the inventory date — and the record must indicate which.

This matters because it fixes the count to a precise moment. If you count at the opening of business, the inventory reflects stock before any of that day’s transactions. If you count at the close of business, it reflects stock after the day’s transactions. Either is acceptable; what is not acceptable is an ambiguous count taken mid-day with drugs moving in and out.

Practical method:

Pick the cut-off — opening or close of business — and stop controlled-substance activity during the count.
Count every container: opened and in-use, unopened stock, and anything set aside for disposal.
Count by schedule. For Schedule II substances, make an exact count or measure. For Schedule III–V, an estimated count is permitted — unless a container holds more than 1,000 tablets or capsules, which requires an exact count. For any opened container, count or measure the actual contents; for a sealed manufacturer container, the labeled count stands.
Reconcile each count against the running log balance. A discrepancy found here is not a clerical annoyance — it can be the first sign of diversion. Stop, investigate, and document.
Write it all down, then sign and date.

What to record on the biennial inventory

The inventory record must be a complete and accurate record of all controlled substances on hand on the inventory date. For each substance, record:

The name of the controlled substance.
The strength and dosage form — for example, 100 mg/mL injectable.
The number of containers or units, and the total quantity in each finished form (exact for Schedule II; an estimated count is permitted for Schedule III–V).
The schedule of the substance.

The record as a whole must also show:

The date the inventory was taken.
Whether it was taken at the opening or close of business.
The name and signature of the person who took it.

A common error is counting only opened, in-use containers and forgetting unopened stock or drugs awaiting disposal. The inventory is everything on hand — every unit the practice is accountable for.

Signing, dating, and retaining the inventory

The inventory is only a valid record once it is signed and dated by the person who performed the count, and marked opening- or close-of-business.

Retention follows the standard controlled-substance rule under 21 CFR 1304.04: keep the completed inventory for at least two years, at the registered practice location, available for DEA inspection. Several states require longer — confirm with your state veterinary board. See how long to keep controlled substance records for the full retention picture.

Practical points that prevent findings:

Keep every past inventory, not just the most recent. An inspector may want to see the chain.
File Schedule II inventory records physically separate from other records, consistent with 21 CFR 1304.04.
Do not discard the old inventory when you take a new one — both stay on file until each is past its retention period.

Inventory vs. running log: two different records

The biennial inventory and the controlled substance log are easy to conflate. They are not the same record and one does not replace the other.

	Biennial inventory	Controlled substance log
What it is	A point-in-time count of everything on hand	A continuous, transaction-by-transaction record
When done	At least every two years, on one date	Updated immediately after every use
Purpose	Establishes a verified baseline	Tracks the chain of custody for each container
Authority	21 CFR 1304.11	21 CFR 1304 (general recordkeeping)

They work together. The biennial inventory sets a verified starting point; the running log tracks every change after it; the next biennial inventory confirms the log stayed accurate. An inspector uses both — the inventory as the anchor, the log as the trail. For the running-log side, see the veterinary controlled substance log pillar guide.

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Frequently asked questions

How often is the biennial inventory required? At least once every two years under 21 CFR 1304.11. It is a maximum interval — you may count more often, and many practices count annually so they are never overdue.

What is the difference between the initial and biennial inventory? The initial inventory is taken once, when the practice first handles controlled substances. The biennial inventory is the recurring count taken at least every two years afterward.

Do I take the inventory at the start or end of the day? Either is acceptable — opening of business or close of business — but the inventory record must clearly state which one you used.

What controlled substances do I count? All of them on hand on the inventory date: opened and in-use containers, unopened stock, and any drugs set aside for disposal. An exact count or measure is required for anything not in a sealed factory container.

How long do I keep the biennial inventory record? At least two years under federal rules (21 CFR 1304.04), at the registered location. Some states require longer — check your state veterinary board.

The inventory is one inspection item among many

A current biennial inventory, signed and on file, is one of the categories a DEA investigator checks — but only one. The same inspection covers your logs, your storage, who has access, your disposal records, and your loss reporting. To see where your practice stands across all of them, work through our DEA inspection checklist for veterinary practices and run the free DEA Self-Audit Checklist.

When the checklist surfaces gaps, the Vet Compliance HQ DEA Controlled Substance Compliance System gives you the inventory forms, logs, SOPs, and training records to close them.

Vet Compliance HQ provides educational compliance resources for veterinary practices. This article is not legal advice. DEA and state requirements change and vary by state — verify current requirements with the DEA and your state veterinary board.