How to Calculate Adjusted COGS: Formula, Inventory, and Example

To calculate the adjusted cost of goods sold, take your beginning inventory, add purchases, direct labor, any indirect costs you’re required to capitalize under Section 263A, and other costs like freight-in, then subtract an ending inventory figure that has already been reduced for shrinkage, damage, obsolescence, and any lower-of-cost-or-market write-downs. The result is the number that flows onto your tax return as COGS and directly reduces your gross profit. The “adjusted” piece is not a separate calculation; it is what happens when each input reflects the real economic cost of your inventory rather than just what the purchase ledger shows.

The Formula and Where It Lands on Your Return

Corporations, S corporations, and partnerships claiming a COGS deduction report the calculation on Form 1125-A.¹ Sole proprietors use Part III of Schedule C, and the arithmetic is identical.² The eight-line structure:

Line 1 — Beginning inventory (last year’s ending inventory)
Line 2 — Purchases, net of returns and discounts
Line 3 — Cost of labor
Line 4 — Additional Section 263A costs
Line 5 — Other costs, including freight-in and containers
Line 6 — Total of lines 1 through 5
Line 7 — Ending inventory (physical count, adjusted)
Line 8 — COGS (Line 6 minus Line 7)

Every adjustment does one of two things: it pushes up the totals on Lines 2 through 5, or it pushes down the ending inventory on Line 7. Both raise Line 8 and cut your taxable gross profit.

What Belongs in Each Cost Line

For merchandise you buy for resale, cost means the invoice price minus trade and quantity discounts, plus freight and other charges to get the goods to your location. For merchandise you produce, cost includes raw materials and supplies, direct labor, and a share of indirect production costs like factory overhead.³

Freight-in belongs in inventory. Shipping you pay to bring goods to your location is part of the cost of those goods and goes on Line 5. Shipping you pay to deliver goods to a customer is a selling expense and stays out of COGS. Mixing the two throws off inventory value and every downstream calculation.

Purchase returns, allowances, and early-payment discounts reduce Line 2. The number you record is what you actually paid net of anything given back.

Section 263A Capitalization

Section 263A, the uniform capitalization rules, requires many businesses to add indirect costs into inventory that never appear on a supplier invoice. These land on Line 4.¹ The categories to look at:

Rent on equipment, facilities, or land used in production or resale
Utilities for production facilities
Insurance on plant, machinery, equipment, or inventory
Depreciation on production equipment and facilities
Repairs and maintenance of production assets
Non-income taxes attributable to production labor, materials, or facilities

The IRS treats these as costs of putting inventory into a sellable condition rather than immediately deductible period expenses.⁴ If you qualify for the small business exemption discussed below, you skip UNICAP entirely.

Adjusting Ending Inventory

Line 7 is where most of the real work happens. If your books show $500,000 in inventory but a physical count finds $470,000 in usable goods, the $30,000 has to be explained. There are three main categories of adjustment.

Shrinkage

Shrinkage covers losses from theft, administrative error, and vendor fraud. Federal rules allow inventory methods that use shrinkage estimates confirmed by a physical count taken after year-end, as long as you normally count each location on a regular basis and correct your estimates when they miss.⁵ Cycle counts, internal loss reports, and security audits are what turn shrinkage into a defensible dollar figure.

Damage and Obsolescence

Goods broken in handling or storage that can’t sell at full price need a write-down. Products that lost value because they were discontinued or overtaken by newer versions also come down. Damage adjustments generally come from warehouse inspection records; obsolescence adjustments come from sales velocity and lifecycle data. Both reduce ending inventory.

Lower of Cost or Market

When the current market value of an inventory item drops below what you paid, you value that item at the lower figure. The comparison must be done item by item; you cannot compare total inventory at cost against total inventory at market and pick whichever is lower. Market value generally means the usual bid price at the inventory date, based on the volume you typically buy. Two carve-outs: the rule does not apply to goods under a firm, non-cancellable sales contract at a fixed price, and it does not apply to inventory accounted for under LIFO, which is always valued at cost.⁶

A Worked Example

Suppose the year’s numbers look like this:

Beginning inventory: $200,000
Purchases, net of returns and discounts: $600,000
Direct labor: $80,000
Section 263A costs: $25,000
Other costs, including freight-in: $15,000
Physical count at year-end: $190,000
Shrinkage identified: $8,000
Obsolescence write-down: $5,000

Add everything on the cost side: $200,000 + $600,000 + $80,000 + $25,000 + $15,000 = $920,000. That’s your cost of goods available for sale.

Now adjust ending inventory. Start with the $190,000 physical count and reduce it by shrinkage and the obsolescence write-down: $190,000 − $8,000 − $5,000 = $177,000.

Subtract adjusted ending inventory from goods available: $920,000 − $177,000 = $743,000. That $743,000 goes on Line 8 of Form 1125-A or the corresponding line of Schedule C.¹ Before finalizing, verify each input against invoices, payroll records, and the count sheets. The IRS expects supporting documents for every number, including sales slips, paid bills, receipts, and deposit slips.⁷

How Your Valuation Method Changes the Answer

Two businesses with identical purchases can produce different adjusted COGS figures because they use different inventory valuation methods. The IRS recognizes three:

FIFO (First In, First Out) assumes the oldest inventory sells first. In a rising-price environment, older, cheaper costs flow out first, producing lower COGS and higher taxable income. FIFO is the IRS default.
LIFO (Last In, First Out) assumes the newest inventory sells first. During inflation, that pushes higher costs into COGS and lowers taxable income. LIFO requires a formal election and comes with a conformity requirement: if you use LIFO on your tax return, you must also use it in your financial statements.⁸
Average Cost uses the weighted average cost of all units available for sale during the period and generally lands between FIFO and LIFO.

Once you pick a method, you stay with it. Changing methods requires filing Form 3115 (Application for Change in Accounting Method) with the return for the year of change.⁹ Many inventory changes qualify for automatic approval without a user fee; some require a non-automatic request reviewed by the National Office. Either way, you calculate a Section 481(a) adjustment that captures the cumulative difference between the old and new methods.

The Small Business Inventory Exemption

Not every business has to run this full process. Under Section 471(c), a small business taxpayer can skip formal inventory accounting and instead treat inventory as non-incidental materials and supplies, deducting the cost when the item is delivered to a customer rather than tracking beginning and ending values.⁵ The same exemption also removes the Section 263A capitalization requirements.

You qualify if your average annual gross receipts for the prior three tax years do not exceed the inflation-adjusted Section 448(c) threshold. For 2026, that threshold is $32 million.² Tax shelters are excluded regardless of size. If your business hasn’t existed for the full three years, you average over the time it has operated, annualizing any short tax years. Switching into this method also uses Form 3115.⁹

Recording It in Your Books

Once the number is finalized, your general ledger has to agree with it. Post a journal entry that debits cost of goods sold and credits inventory for the total of the adjustments (shrinkage, damage, obsolescence). That brings the ledger balance in line with your physical count. If you’re changing your inventory method for the current tax year, you also restate the prior year’s closing inventory under the new method and report the difference through a Section 481(a) adjustment.¹ Both Form 1125-A and Schedule C ask you to identify your valuation method and whether it changed during the year.

What Inaccurate Numbers Cost You

Inventory errors flow straight into COGS and from there into taxable income. An overstated ending inventory understates COGS and overpays tax. An understated ending inventory does the opposite, and the IRS treats that as an underpayment.

The standard accuracy-related penalty is 20% of the underpayment attributable to negligence or a substantial understatement of income tax. A substantial understatement exists when the understatement exceeds the greater of 10% of the tax that should have been shown on the return or $5,000. For inventory in particular, the IRS also watches valuation misstatements: claiming an inventory value at 150% or more of the correct amount triggers the 20% penalty, and a misstatement of 200% or more doubles it to 40%.¹⁰

Documentation is what makes an audit routine instead of expensive. Keep the physical count worksheets, the shrinkage calculations, the purchase invoices, and the analysis behind every write-down. Showing the work is how the number on Line 8 stops being a number and starts being a defensible position.

1
Internal Revenue Service. Form 1125-A – Cost of Goods Sold
2
Internal Revenue Service. Instructions for Schedule C (Form 1040)
3
eCFR. 26 CFR 1.471-3 – Inventories at Cost
4
eCFR. 26 CFR 1.263A-1 – Uniform Capitalization of Costs
5
Office of the Law Revision Counsel. 26 USC 471 – General Rule for Inventories
6
Internal Revenue Service. Publication 538, Accounting Periods and Methods
7
Internal Revenue Service. What Kind of Records Should I Keep
8
Internal Revenue Service. Practice Unit – LIFO Conformity
9
Internal Revenue Service. Instructions for Form 3115
10
Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments