Inventory Costing Methods for Manufacturers

Manufacturers can use four inventory costing methods under U.S. GAAP: first-in, first-out (FIFO), last-in, first-out (LIFO), weighted-average cost, and specific identification. Each method is a rule that determines which costs flow to cost of goods sold when a unit is sold and which costs remain on the balance sheet as ending inventory. The choice of method does not change the physical movement of goods, only the accounting cost assigned to each unit, and that distinction has direct consequences for reported profit, ending inventory, and, in the case of LIFO, the taxes a manufacturer actually pays.

The Four Inventory Costing Methods, Defined

Understanding what each method does mechanically is the starting point for any method-selection analysis.

FIFO (First-In, First-Out)

FIFO assumes the first units acquired are the first units sold. Cost of goods sold reflects the oldest purchase costs in inventory, and ending inventory carries the most recent costs. For most manufacturers, FIFO mirrors the actual physical movement of goods, especially for materials subject to obsolescence or shelf-life constraints, which is part of why it is the most widely used method globally.

LIFO (Last-In, First-Out)

LIFO assumes the last units acquired are the first units sold. Cost of goods sold reflects the newest, most recent costs, while ending inventory carries the oldest costs. This rarely matches the physical flow of goods. LIFO is also a uniquely American phenomenon: it is permitted under U.S. tax law and U.S. GAAP but explicitly prohibited under International Financial Reporting Standards (IFRS IAS 2), making it unavailable to manufacturers that report under IFRS.

Weighted-Average Cost

Weighted-average cost pools all available inventory costs and divides by total units to produce a single blended cost per unit. That average applies to both units sold and units remaining in ending inventory. In a perpetual inventory system, this is often called the moving-average method because the average recalculates after each purchase. The method is common in ERP systems because it smooths price volatility without requiring layer-by-layer tracking.

Specific Identification

Specific identification tracks the actual, individual cost of each unit sold and each unit remaining in inventory. It is the most precise approach but is only practical for high-value, low-volume, serialized goods, such as custom machinery, aircraft components, or specialized tooling. For a manufacturer moving thousands of interchangeable raw-material units, specific identification is operationally unworkable.

How Each Method Affects COGS, Ending Inventory, and Taxes

The four methods produce identical results when unit costs are stable. The differences emerge only when purchase prices change over time.

A Numerical Illustration

Suppose a manufacturer purchases 100 units of a key component at $10 per unit in January, 100 units at $12 in June, and 100 units at $14 in November, then sells 200 units during the year. Total cost available is $3,600.

• FIFO: COGS = (100 x $10) + (100 x $12) = $2,200. Ending inventory = 100 x $14 = $1,400.
• LIFO: COGS = (100 x $14) + (100 x $12) = $2,600. Ending inventory = 100 x $10 = $1,000.
• Weighted-average: Average cost = $3,600 / 300 = $12.00 per unit. COGS = 200 x $12 = $2,400. Ending inventory = 100 x $12 = $1,200.

In this rising-cost scenario, FIFO produces the lowest COGS and highest ending inventory, LIFO produces the highest COGS and lowest ending inventory, and weighted-average lands between the two. Total cost recognized across COGS and ending inventory is $3,600 under all three methods; the difference is purely one of timing.

Tax Consequences

Those COGS figures flow directly through to pretax income and therefore to taxable income. Higher COGS means lower taxable income, so during periods of cost inflation, LIFO produces the smallest current tax bill while FIFO produces the largest. This tax deferral is the primary reason manufacturers with large, stable inventories evaluate LIFO during periods of persistent input-cost increases, such as tariff cycles or commodity-driven price spikes.

In a deflationary environment, the results invert. FIFO expenses the older, higher costs first, producing higher COGS, lower profit, and lower current tax. LIFO expenses the newer, lower costs first, producing lower COGS and a higher current tax bill. The practical takeaway is that FIFO and LIFO trade positions depending on the direction of price movement, while weighted-average consistently dampens both swings because it distributes cost changes across all units.

The Tax Rules: LIFO Election, Conformity, and Liquidation Risk

LIFO’s appeal to manufacturers is almost entirely a tax story, and that story comes with meaningful strings attached.

The LIFO Election

A manufacturer that wants to use LIFO for federal tax purposes must elect the method by filing IRS Form 970, Application to Use LIFO Inventory Method. The election must be made with the tax return for the first year in which the company wants to apply LIFO.

The Conformity Rule

Under Internal Revenue Code Section 472(c), a taxpayer that uses LIFO for tax purposes must also use LIFO in any income statement issued to shareholders, partners, creditors, or other external parties for that same year. There is no option to report higher FIFO or average-cost earnings to lenders and investors while simultaneously claiming the lower LIFO income on the tax return. This book-tax conformity requirement can affect loan covenants, bonding capacity, and investor perception because LIFO depresses both reported earnings and reported inventory values during inflationary periods.

LIFO Liquidation

The deferral LIFO provides is real but not permanent. When a manufacturer draws down inventory quantities below prior-year levels, cost of goods sold must include costs from older, lower-cost inventory layers. This event, known as a LIFO liquidation, can spike taxable income in a single year and erase years of accumulated tax deferral. Manufacturers considering LIFO should model their inventory quantity patterns carefully, because the timing and size of a potential liquidation is where most of the planning risk sits.

Changing Methods

Manufacturers already using a costing method and considering a switch face an additional hurdle. Changing an inventory costing method for federal tax purposes generally requires consent from the IRS, filed on Form 3115, Application for Change in Accounting Method. Some inventory changes are processed as automatic method changes, while others are non-automatic and require advance IRS approval. Under GAAP, a method change must also be disclosed and is generally applied retrospectively under ASC 250, which adds financial-statement complexity to what might otherwise appear to be a straightforward tax decision.

GAAP Measurement Rules by Method

Selecting a cost-flow method is only part of the inventory accounting picture. U.S. GAAP also requires manufacturers to apply a subsequent-measurement rule to determine whether inventory should be written down below its recorded cost.

Under FASB Accounting Standards Update 2015-11, most companies now measure inventory at the lower of cost and net realizable value (NRV), where NRV is the estimated selling price less reasonably predictable costs of completion and disposal. However, ASU 2015-11 specifically excludes inventory measured using LIFO or the retail inventory method from this simplified rule. Manufacturers on LIFO remain on the older lower-of-cost-or-market test, where market means current replacement cost subject to a floor and ceiling defined by NRV. The costing method a manufacturer selects therefore determines not only how cost flows but also which subsequent-measurement standard governs future writedowns.

LIFO users also carry a distinct disclosure obligation. Under ASC 330-10-50, companies that use LIFO must disclose the LIFO reserve, which is the difference between LIFO inventory and what inventory would have been under FIFO or average cost. This disclosure allows financial statement readers and analysts to make meaningful comparisons across companies using different methods, and it is one reason auditors pay close attention to LIFO reserve calculations during an inventory-focused audit or assurance engagement.

How Manufacturers Should Choose

No single method is right for every manufacturer. The analysis starts with the reporting framework and works through cost trends, operational realities, and strategic context.

Start with your reporting framework. If your company reports or expects to report under IFRS, LIFO is off the table entirely. The remaining choice is among FIFO, weighted-average, and specific identification.

Consider your cost trends and inventory profile. Manufacturers with fast-turning, perishable, or seasonally changing inputs often find that FIFO produces a balance sheet inventory value close to current replacement cost, which lenders and buyers prefer. Manufacturers with large, stable raw-material inventories facing prolonged input-cost inflation are the classic LIFO candidates, because the tax deferral is large enough to justify the conformity constraint and the recordkeeping burden.

Factor in your business horizon. A company being positioned for a sale or seeking outside capital faces complications from LIFO’s suppressed earnings and inventory values. Transaction advisory work frequently involves unwinding or evaluating LIFO reserves because acquirers and lenders want to understand what the inventory is actually worth at current costs. If a liquidity event is within a planning horizon of a few years, the tax benefits of LIFO may not outweigh the friction it creates in due diligence.

Match the method to your goods. Specific identification is appropriate only when individual units are distinguishable and material enough to justify the tracking cost. Weighted-average is a practical default for commodity-like raw materials where units are interchangeable and no method offers a decisive edge. The right method is the one that fits your cost trend, your tax strategy, your reporting obligations, and the nature of the goods you actually manufacture and sell.

Manufacturers who build financial reporting disciplines around a chosen costing method, consistently applied and well-documented, will encounter far fewer complications at audit time than those who treat the election as an afterthought.

Related reading: Manufacturing Accounting: Is Standard Costing GAAP-Compliant?

Frequently Asked Questions

What inventory costing methods can manufacturers use?

Under U.S. GAAP, manufacturers can use four methods: FIFO (first-in, first-out), LIFO (last-in, first-out), weighted-average cost, and specific identification. All four are permitted under ASC 330. Manufacturers reporting under IFRS have three options, since IAS 2 prohibits LIFO.

Which inventory costing method is best for a manufacturer during inflation?

During sustained cost inflation, LIFO produces the highest cost of goods sold and the lowest current taxable income, deferring tax and preserving cash. FIFO does the opposite, reporting higher profit and a larger current tax bill but a balance sheet inventory figure closer to current replacement cost. Whether LIFO is worth it depends on whether the tax deferral outweighs the conformity rule, the recordkeeping burden, the risk of a future LIFO liquidation, and any financing or transaction considerations.

Is LIFO allowed under GAAP and IFRS?

LIFO is permitted under U.S. GAAP (ASC 330) and U.S. federal tax law (IRC Section 472) but is prohibited under IFRS (IAS 2). Manufacturers that report under IFRS, or that expect to transition to IFRS, must use FIFO, weighted-average, or specific identification.

What is the LIFO conformity rule?

Under Internal Revenue Code Section 472(c), a manufacturer that uses LIFO for tax purposes must also use LIFO in the financial statements it issues to shareholders, creditors, and other external parties. You cannot show higher FIFO or average-cost earnings to lenders while claiming lower LIFO income on the tax return. This requirement can affect loan covenants, bonding, and investor perception.

How does weighted-average costing work for manufacturers?

Weighted-average cost divides the total cost of all inventory available for sale by the total number of units available to produce a single blended cost per unit. That rate is applied to both units sold (COGS) and units remaining (ending inventory). In a perpetual system, the average recalculates after each purchase, which smooths the effect of price changes across reporting periods.

Can a manufacturer change its inventory costing method?

Yes, but the process has requirements on both the tax and financial reporting sides. Changing a costing method for federal tax purposes generally requires IRS consent, filed on Form 3115. Under GAAP, method changes must be disclosed and are typically applied retrospectively under ASC 250. Most manufacturers change methods only when there is a substantive tax or business reason because the administrative and financial-statement costs can be significant.