Veterinary Drug and Supply Inventory: Accounting and Tax Treatment

Drugs and supplies are usually the second-largest expense in a veterinary practice, behind only payroll (equipment is typically third, and it gets its own accounting treatment, covered in our guide on Section 179 and bonus depreciation for veterinary equipment). Vaccines, antibiotics, anti-parasitics, anesthetics, NSAIDs, heartworm preventives, surgical supplies, and lab consumables flow through the clinic every day, and the way the practice accounts for that flow directly affects taxable income, cash flow, and how much time gets burned on bookkeeping. The tax code offers most veterinary practices a genuinely simpler path than what large manufacturers or retailers face, because the uniform capitalization rules that complicate inventory accounting for big businesses do not apply to practices under the small business gross receipts threshold. But many practices either over-engineer their inventory system (treating every syringe like a widget in a factory) or ignore it entirely, and both mistakes cost money.

How should a vet practice track drug and supply inventory?

The answer depends on whether you are asking about tax compliance or operational management, because the two have different requirements and the tax rules are more forgiving than most practice owners realize.

For tax purposes, a veterinary practice that meets the gross receipts test under IRC 448(c) (average annual gross receipts of $32 million or less for tax years beginning in 2026, measured over the prior three tax years) can use the cash method of accounting and is not required to maintain formal inventories at all. Instead, the practice can treat drugs and supplies as “non-incidental materials and supplies” under IRC 471, which means the cost is deductible when the item is used or consumed in providing veterinary services, not when it is purchased and placed on the shelf. Practically every standalone veterinary practice falls well under the $32 million threshold, and even multi-location groups rarely approach it.

For operational purposes, however, a practice still needs to know what is on the shelf, what is running low, and what is approaching expiration. Most modern practice management systems (Cornerstone, eVetPractice, Shepherd, Covetrus Pulse) include inventory modules that track quantities on hand, reorder points, and lot-level expiration dates. The discipline of using these modules consistently is what keeps the practice from discovering it has $15,000 in expired heartworm preventives in a back closet. Operational inventory discipline and tax inventory accounting are not the same thing, and the tax rules do not force a small veterinary practice to run the kind of formal perpetual inventory system that a large retailer or manufacturer must maintain.

What is cost of goods sold for a vet practice?

Cost of goods sold (COGS) is the direct cost of the drugs, supplies, and materials consumed in delivering veterinary services during the tax year: pharmaceuticals administered or dispensed, vaccines given, surgical consumables used during procedures, lab reagents consumed in diagnostic testing, and medical supplies like bandaging, sutures, and IV fluids.

Whether a veterinary practice reports a formal COGS line on its tax return depends on its accounting method. A practice on the accrual method that maintains formal inventories will compute COGS using the standard formula: beginning inventory plus purchases minus ending inventory. A practice using the cash method under the small business exception does not compute COGS in the traditional sense; instead, it deducts the cost of materials and supplies when they are used or consumed, which achieves roughly the same economic result over time but without the year-end physical count that drives the formal calculation.

For internal management, every practice should know its drug and supply cost as a percentage of revenue regardless of the tax method. Industry benchmarks for veterinary practices typically place drug and supply costs at 18% to 22% of total revenue, depending on the service mix. A practice that dispenses a high volume of pharmaceuticals (heartworm and flea/tick preventives, chronic medications) will run toward the higher end. Tracking this ratio month to month is one of the simplest indicators of whether drug pricing, purchasing, and waste are under control. The same discipline shows up in other supply-heavy practices; our guide on dental practice equipment and supply deductions covers the analogous cost-tracking questions for a different professional practice.

What is UNICAP, and why are vet practices exempt?

The uniform capitalization rules under IRC 263A generally require businesses that produce or resell goods to capitalize certain direct and indirect costs (storage, handling, purchasing department overhead, portions of administrative cost) into the cost of inventory rather than deducting them immediately. For a manufacturer with a warehouse full of partially completed goods, UNICAP forces those absorption costs into the inventory value on the balance sheet, deferring the deduction until the goods are sold.

Veterinary practices are almost universally exempt because they meet the small business exception tied to IRC 448(c). The threshold for tax years beginning in 2026 is $32 million in average annual gross receipts, measured over the three preceding tax years. The vast majority of veterinary practices generate between $500,000 and $5 million in annual revenue, and even the largest multi-doctor groups rarely approach $32 million. The exception removes the obligation to capitalize indirect costs into inventory, which means the practice does not need to track and allocate storage costs, purchasing overhead, or facility costs to the inventory sitting on its shelves.

This exemption is one of the most valuable simplification provisions in the code for veterinary practices. It means the practice can use the cash method, skip formal inventory accounting for tax purposes, and deduct the cost of drugs and supplies when consumed. The alternative, full accrual-basis accounting with UNICAP, would require a level of cost allocation that makes no practical sense for a business buying pre-manufactured pharmaceuticals and administering them to patients.

How are expired or damaged drugs handled for tax purposes?

Drug expiration is a routine fact of veterinary practice. Vaccines ordered for an outbreak that didn’t materialize, antibiotics that sat on the shelf past their use-by date, or controlled substances that must be destroyed because they can’t be returned all represent inventory that can no longer be used at its original value.

Under Reg 1.471-2(c), goods that are unsalable at normal prices or unusable in the normal way because of damage, imperfections, shop wear, changes of style, odd or broken lots, or other similar causes may be valued below cost. For a practice on the accrual method, expired drugs should be written down to net realizable value (often zero, since expired pharmaceuticals have no resale market and cannot legally be administered) when the year-end inventory is valued. That write-down reduces ending inventory, increases COGS, and reduces taxable income in the year the write-down is taken.

For a practice using the cash method, the mechanics differ slightly but the result is similar. If the practice deducts drug costs when consumed, an expired drug that was never administered has not yet been deducted. The practice can deduct the cost when the expired drug is identified as unusable and removed from service. The important thing is to document the write-off: the item, the quantity, the acquisition cost, the reason for disposal (expiration, contamination, damage), and the date it was removed from the shelf. If the item is a controlled substance, the documentation requirements are more extensive, as discussed below.

Veterinary practices can reduce expiration losses through basic purchasing discipline: ordering smaller quantities more frequently rather than chasing volume discounts on drugs with short shelf lives, rotating stock by expiration date (first-expiring, first-out), and reviewing slow-moving items quarterly rather than discovering them during an annual cleanup.

What special rules apply to controlled substance inventory?

Veterinary practices that stock and administer controlled substances (DEA Schedule II through V) are subject to federal record-keeping requirements under 21 CFR Part 1304 that go well beyond normal inventory tracking. These requirements exist for regulatory compliance, not for tax purposes, but they create a record-keeping discipline that doubles as excellent tax documentation.

DEA-registered practices must maintain a biennial (every two years) physical inventory of all controlled substances on hand, and many practices conduct annual inventories voluntarily because the biennial cycle leaves too long a gap for detecting discrepancies. The inventory must record the name of each substance, the finished form (tablets, injectables, patches), the number of units or volume, and the date and time of the count. For Schedule II substances (which in veterinary practice commonly include certain opioid analgesics and euthanasia solutions containing pentobarbital), records must be maintained separately from other controlled substance records.

The practice must also maintain ongoing dispensing and administration logs that track every use of every controlled substance: the patient, the date, the quantity, and the prescribing veterinarian. These logs, combined with purchase records and periodic physical counts, create a closed-loop system where every unit can be traced from receipt to use or disposal.

When controlled substances expire or need to be destroyed, the practice cannot simply throw them away. DEA regulations require witnessed, documented destruction, typically through a reverse distributor (a DEA-registered entity that accepts and destroys controlled substances). The cost of destroyed controlled substances is deductible under the same rules as any other expired inventory, but the documentation standard is higher, and destruction records should be retained indefinitely as part of the practice’s DEA compliance file.

How do purchasing and inventory valuation affect taxes?

Because most veterinary practices on the cash method deduct drug costs when items are used or consumed (not when purchased), buying a large quantity of drugs at year-end does not automatically accelerate the deduction into the current year. The deduction happens when the drugs come off the shelf and into the patient, not when the distributor’s invoice is paid. That said, a practice can elect to treat inventories using the method that conforms to its financial accounting treatment, and if the practice’s books deduct supplies when purchased, the IRS will generally accept that treatment for a qualifying small business. The specific election and its boundaries are worth discussing with the practice’s CPA.

From a cash flow perspective, purchasing decisions should be driven by clinical need, expiration risk, and supplier pricing, not by tax timing. Buying six months of a slow-moving injectable to capture a 5% volume discount makes no sense if 30% of the order expires before it gets used. Smaller, more frequent orders with tighter expiration management almost always produce better net results than bulk purchasing for marginal discounts, particularly for biologics (vaccines) and compounded medications with shorter shelf lives.

For practices that do maintain formal inventories (either because they are on the accrual method or because they want the management visibility), the two common valuation methods are cost and lower of cost or market (LCM). Under LCM, if a drug’s wholesale price drops or an item approaches expiration, the practice can write the inventory value down to the lower market price and recognize the loss immediately. This intersects with the Reg 1.471-2(c) write-down rule: goods that are unsalable or unusable can be valued below cost. In practice, veterinary drug prices have generally trended upward, so LCM rarely produces a meaningful benefit over straight cost for most drug categories. Where it matters most is for items approaching expiration or items that have become obsolete because a newer product has replaced them in the clinic’s formulary.

What records support inventory deductions?

Whether the practice uses formal inventories or the non-incidental materials and supplies treatment, the IRS expects documentation sufficient to support the deductions claimed. For a veterinary practice, that means:

• Purchase invoices from distributors and manufacturers, showing items, quantities, unit prices, and dates received.
• Dispensing and administration records from the practice management system, showing which drugs were used on which patients and when.
• Year-end inventory counts (if formal inventories are maintained) or periodic physical counts for operational purposes.
• Expired inventory disposal logs, showing item, quantity, acquisition cost, reason for disposal, and date removed from service.
• Controlled substance records required by DEA regulations, including biennial inventories, dispensing logs, and destruction documentation.
• Supplier credit memos for returned merchandise.

These records should be retained for at least seven years, and indefinitely for controlled substance documentation.

How does inventory factor into selling a practice?

When a veterinary practice is sold, inventory is typically a separate line item in the purchase agreement, valued at cost (or at a negotiated value for slow-moving or near-expiration items). The buyer wants to know what is on the shelf, what it cost, what is close to expiring, and what the controlled substance inventory looks like, because all of that affects the purchase price allocation and post-closing operations.

From the seller’s perspective, inflated or poorly documented inventory creates problems at due diligence. A shelf full of expired drugs that has never been written off inflates the reported inventory value and, for accrual-method practices, may have understated COGS and overstated income in prior years. Cleaning up the inventory before a sale (writing off expired items, reconciling controlled substance logs, producing accurate counts by category) is part of getting the practice ready, and it is much better done a year before the sale than during the buyer’s due diligence. For the broader tax picture of buying or selling a veterinary practice, including purchase price allocation and goodwill, see the valuation and sale guide.

What should I do next?

The single highest-value step for most veterinary practices is confirming that the practice qualifies for the small business exception under IRC 448(c) and is actually using the simplified method it is entitled to. A surprising number of practices maintain formal inventory records and compute COGS the hard way because their accountant set it up years ago without revisiting whether the practice qualifies for the easier treatment. If the practice’s average gross receipts over the prior three years are under $32 million (and they almost certainly are), the practice can use the cash method, treat inventory as non-incidental materials and supplies, and skip UNICAP entirely.

The second step is getting expired inventory off the books. Document the disposal, take the write-off, and set up a quarterly review process so expired items are caught within 90 days instead of sitting on the shelf until the next annual cleanup.

How the inventory deduction actually lands on your return also depends on how the practice is structured. For a pass-through entity, the cash-method treatment described above flows to the owner’s individual return the same way other business deductions do, which is one more reason to get the entity choice right before layering on accounting-method decisions. Our guide on veterinary practice entity structure covers how LLC, S-corp, and PC elections interact with pass-through deductions.

Related guides:

• Buying or Selling a Veterinary Practice: Valuation, Goodwill, and Tax Planning
• Veterinary Equipment Depreciation: Section 179 and Bonus Depreciation
• Mobile Veterinary Clinic and Telemedicine Tax Deductions
• Specialty and Emergency Veterinary Hospital Tax Issues

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.