An inventory adjustment is a correction to your accounting records that brings the recorded quantity or value of your stock into line with what physically exists. Businesses carry inventory as an asset, but theft, damage, counting mistakes, and obsolescence pull the books out of sync with the shelves. The adjustment closes that gap, and it matters to two audiences at once: the people running the business and the IRS, which uses your inventory figures to calculate cost of goods sold and, ultimately, how much tax you owe.
What Causes an Inventory Adjustment
Shrinkage is the catch-all term for goods that vanish without producing revenue. Shoplifting, employee theft, and vendor fraud all leave the books showing more stock than actually exists. These losses stay invisible until someone counts.
Damage and spoilage push goods off the saleable shelf. A forklift clips a pallet, a freezer fails overnight, or raw materials sit past their usable life. The items are still there physically but can no longer be sold at normal prices. IRS rules require you to value these goods at their realistic selling price minus the direct cost of disposing of them, even when the rest of your inventory uses a different valuation method.
Administrative errors are the mundane cause and probably the most common. A receiving clerk enters the wrong quantity, a barcode scans twice, or a return gets credited to the wrong SKU. Small mistakes compound if no one catches them.
Obsolescence hits when products lose market value while sitting in storage. Technology moves forward, fashion shifts, or a manufacturer releases a newer model. The goods are physically fine, but nobody wants them at the original price. Accounting standards require a write-down to reflect that diminished value rather than carrying the items at full cost.
How the Adjustment Hits Your Financial Statements
When physical stock comes up short of what the books show, the correction flows through two statements at once. On the balance sheet, the inventory asset account decreases. On the income statement, cost of goods sold (COGS) increases by the same amount, because those missing or damaged goods consumed value without generating revenue.
Higher COGS means lower gross profit, which means lower taxable income for the period. That sounds like good news, but consistently large adjustments signal weak controls. Lenders, investors, and auditors read frequent write-downs as evidence that a company has lost track of its physical assets.
Timing matters more than people expect. Discover a $200,000 shrinkage loss in January but delay recording it until December, and every interim financial report overstates assets and understates COGS. Discrepancies that land in the wrong fiscal period distort performance metrics and create problems during audits.
Valuation Rules That Set the Dollar Amount
The size of any adjustment depends partly on how you value your stock. The IRS generally permits three methods: cost, lower of cost or market, and the retail method. Whichever you choose must conform to generally accepted accounting principles for your type of business and must clearly reflect income. You cannot switch methods year to year without following a formal change procedure.
Cost, FIFO, and LIFO
Under the cost method, you value inventory at what you paid for it, including direct and indirect acquisition costs. You still need a flow assumption to decide which units are treated as sold first. First-in, first-out (FIFO) assumes the oldest inventory goes first; last-in, first-out (LIFO) assumes the newest does. When prices are rising, LIFO charges higher-cost recent purchases to COGS, which lowers taxable income, while FIFO produces higher reported earnings and a bigger tax bill.
One constraint on LIFO: if you elect it for tax purposes, the IRS requires you to also use LIFO in your financial reports to shareholders and other stakeholders. You cannot show investors a rosier FIFO picture while claiming LIFO’s tax benefit.
Write-Downs for Damaged, Obsolete, or Devalued Goods
When inventory loses value due to damage, obsolescence, or falling market prices, GAAP requires a write-down rather than continued carrying at full cost. For businesses using FIFO or average cost, the current standard is “lower of cost or net realizable value,” where net realizable value is the estimated selling price minus the costs to complete and sell the item. For businesses using LIFO or the retail inventory method, the older “lower of cost or market” framework still applies, using replacement cost bounded by a ceiling and floor. Once inventory is written down under U.S. GAAP, that lower figure becomes the new cost basis, and reversals are not permitted.
For tax purposes, the IRS also allows the lower of cost or market method. Goods that cannot be sold at normal prices because of damage, imperfections, style changes, or similar causes are valued at their realistic selling price minus direct disposal costs, regardless of which method covers the rest of your inventory.
How to Report It on a Federal Tax Return
Inventory adjustments do not appear on their own line. They show up embedded in your beginning and ending inventory figures, which feed the cost of goods sold calculation.
Corporations, S corporations, and partnerships that deduct cost of goods sold file Form 1125-A. Beginning inventory goes on Line 1, ending inventory on Line 7, and the resulting COGS on Line 8. That Line 8 figure flows into the entity’s main return (Form 1120, 1120S, or 1065). If you changed your inventory accounting method during the year, you must refigure the prior year’s closing inventory under the new method and report any difference as a Section 481(a) adjustment.
Sole proprietors report COGS in Part III of Schedule C (Form 1040). The structure is the same: beginning inventory, plus purchases and labor, minus ending inventory equals COGS. Even taxpayers who qualify for the small business exemption and choose not to keep a formal inventory still need a method that clearly reflects income.
The Small Business Exemption Under Section 471(c)
Not every business has to run traditional inventory accounting for tax purposes. Under IRC Section 471(c), businesses that meet the gross receipts test can skip the accrual-based inventory rules. For tax years beginning in 2026, the exemption applies if your average annual gross receipts over the preceding three tax years do not exceed $32 million.
If you qualify, you have two options. You can treat inventory items as non-incidental materials and supplies, deducting their cost when you first use or sell them rather than capitalizing them. Or you can follow whatever inventory method is reflected in your audited financial statements, or if you have no audited financials, your own books and records.
Switching to this method from traditional inventory accounting creates a Section 481(a) adjustment. Positive adjustments, where the change increases taxable income, are generally spread over four years. Negative adjustments that decrease taxable income are taken entirely in the year of the change.
Documentation That Will Survive an Audit
Every inventory adjustment needs a paper trail. At minimum, record the date of the count, the name of the person who performed the physical verification, the specific location (bin, shelf, or warehouse zone), the SKU or item identifier, the recorded quantity versus the actual quantity, the unit cost, and a reason code explaining the discrepancy. Common reason codes cover damage, theft, count error, and obsolescence.
Those details go on an inventory count sheet or formal discrepancy report, which serves as the source document for the accounting entry. Keep the report in your permanent records. Auditors will want to trace any adjustment back to the physical event that caused it.
Digital systems add another layer. Enterprise resource planning (ERP) and inventory management platforms should automatically generate time-stamped audit logs whenever someone creates, modifies, or deletes an inventory record. The log should capture user ID, timestamp, and what changed. That metadata makes unauthorized adjustments harder to hide and gives auditors a reliable trail.
Separation of Duties
The single most important control over inventory adjustments is making sure the person who counts the stock is not the same person who records the adjustment in the system. That is where fraud tends to happen: an employee takes inventory, then adjusts the records to cover the shortage. Separating the roles breaks the chain.
A sound setup uses at least three people: one handles the physical count, a second enters the adjustment into the accounting system, and a third reviews and approves the entry. If you only have two available, both should review each other’s work. Whoever has physical access to inventory should never also be able to post unsupervised entries to the general ledger.
After data entry, a supervisor or auditor should review and approve the entry, either through an electronic signature in the system or a physical sign-off on the discrepancy report. That final review catches honest mistakes and deliberate manipulation before the numbers become part of your official records.
Penalties for Getting It Wrong
Inventory errors that cause you to understate tax liability can trigger the IRS accuracy-related penalty. The penalty applies when there is a “substantial understatement” of income tax, which for most taxpayers means the understatement exceeds the greater of 10% of the tax that should have been shown on the return, or $5,000. For corporations other than S corporations, the threshold is the lesser of 10% of the correct tax (or $10,000 if greater), or $10 million. The penalty itself is 20% of the portion of the underpayment attributable to the understatement.
The $5,000 figure is not the fine. It is the threshold that decides whether the understatement is large enough for the penalty to apply. The actual cost is 20% of the underpaid tax. If sloppy inventory records caused you to underreport $50,000 in income, the penalty on the resulting tax underpayment adds up quickly.
In extreme cases involving willful tax evasion, the consequences turn criminal. Under 26 U.S.C. ยง 7201, anyone who willfully attempts to evade or defeat a tax faces a felony conviction carrying up to five years in prison and fines of up to $100,000 ($500,000 for corporations), plus the costs of prosecution. Intentionally inflating inventory losses to reduce taxable income falls within that statute.
Accurate, well-documented adjustments are the best defense during an examination or audit. When every entry ties back to a count sheet, a reason code, and a supervisor’s approval, the conversation with the IRS stays short.