Inventory valuation is deciding what your stock is worth, and what cost to charge against each sale.
The question only becomes difficult when prices change. If you bought the same product twice at different prices and then sold one, which price applies? The answer is a choice, made once and applied consistently, and it affects your reported profit, your tax and the value of the stock on your balance sheet.
Two things are worth establishing before the detail. First, this is an accounting decision, not a warehouse instruction — how you value stock and how you physically rotate it are separate. Second, the choice is usually constrained by your reporting standard rather than genuinely open.
The four main methods
FIFO — First In, First Out. The cost of the oldest stock is charged against sales. What remains is valued at the most recent purchase prices.
LIFO — Last In, First Out. The cost of the newest stock is charged against sales. What remains is valued at older prices.
Weighted average cost (WAC). All purchases go into a pool and every unit sold is charged the running average. Also called AVCO.
Specific identification. Each individual unit carries its own actual cost. Used where units are genuinely distinguishable and valuable — vehicles, jewellery, machinery, art.
A fifth method appears in retail and is worth naming: the retail method, which estimates cost by applying a cost-to-retail ratio to the selling value of stock. It is an approximation used where counting cost per line is impractical across a large, fast-changing range.
One example, four results
Say you buy the same product twice and then sell 120 units:
- January: 100 units at $8 each
- March: 100 units at $10 each
Total purchased: 200 units for $1,800.
FIFO — cost the oldest first: 100 at $8 ($800) plus 20 at $10 ($200). Cost of goods sold $1,000. Closing stock 80 units at $10 = $800.
LIFO — cost the newest first: 100 at $10 ($1,000) plus 20 at $8 ($160). Cost of goods sold $1,160. Closing stock 80 units at $8 = $640.
Weighted average — average cost is $1,800 ÷ 200 = $9 per unit. Cost of goods sold 120 × $9 = $1,080. Closing stock 80 × $9 = $720.
Specific identification — depends entirely on which physical units you sold. If you happened to ship 60 from each batch, cost of goods sold is (60 × $8) + (60 × $10) = $1,080.
Same 120 units gone, same 80 units on the shelf, and a $160 spread in reported cost of goods sold. If you sold those units for $15 each — $1,800 revenue — gross profit reads $800 under FIFO, $720 under weighted average, and $640 under LIFO.
Setting the four side by side makes the spread obvious:
| Method | How it costs the sale | Cost of goods sold | Ending inventory | Gross profit on $1,800 revenue |
|---|---|---|---|---|
| FIFO | Oldest costs first | $1,000 | $800 | $800 |
| Weighted average | Every unit at the blended cost | $1,080 | $720 | $720 |
| Specific identification | The actual units shipped | $1,080 | $720 | $720 |
| LIFO | Newest costs first | $1,160 | $640 | $640 |
Read down the cost of goods sold column and the pattern is the whole argument: in a rising market FIFO reports the lowest cost, the highest profit and the most current stock value, LIFO reports the reverse, and weighted average sits between them. Nothing about the business changed between those four rows.
How each method affects your numbers
In a period of rising prices:
- FIFO — lowest cost of goods sold, highest reported profit, highest tax, closing stock closest to replacement cost.
- LIFO — highest cost of goods sold, lowest reported profit, lowest tax, closing stock increasingly out of date.
- WAC — sits between the two on every measure.
In a period of falling prices these reverse. FIFO reports the higher cost and lower profit; LIFO the opposite. Neither method has an inherent bias — they simply track whichever direction your purchase prices are moving, and the conventional description of LIFO as “the tax-efficient one” assumes inflation.
The balance sheet effect deserves separate attention. Under FIFO, closing stock reflects recent purchases, so the figure means something. Under LIFO in a long-established business, closing stock can carry costs from many years earlier, and the balance sheet value bears little relation to what the goods would cost to replace.
The constraint that decides it for most businesses
LIFO is prohibited under IFRS, the accounting standard used across most of the world. It is permitted under US GAAP.
So for the majority of businesses the real choice is between FIFO and weighted average, and the LIFO debate is academic.
In the United States, LIFO carries an additional condition — the conformity rule. If you use LIFO for tax, you must also use it in your financial statements. You cannot report strong profits to investors and weak profits to the tax authority. That trade-off is why many eligible US businesses still choose FIFO.
There is also LIFO liquidation to be aware of. If you sell more than you buy in a period, LIFO forces you into old, cheap cost layers. Cost of goods sold drops, profit spikes, and a large tax bill arrives in a year when you were probably running stock down because trading was difficult.
How to choose
Under IFRS, choose between FIFO and weighted average.
Pick FIFO if your goods are perishable or dated, if you want a closing stock value close to replacement cost, or if comparability with competitors matters. It is the most common choice and the easiest to explain.
Pick weighted average if your stock is homogeneous and interchangeable — fasteners, chemicals, fuel, commodity materials — where tracking cost layers is administrative effort without insight. It also smooths the effect of a single expensive purchase, which suits volatile input prices.
Under US GAAP, LIFO becomes available and is a finance decision rather than a warehouse one. Model it against your actual purchase history. Significant stock holding plus sustained inflation can make the tax deferral worth the conformity constraint and the weaker balance sheet.
Use specific identification where units are individually identifiable and valuable enough to justify tracking. It is the most accurate method and impractical for anything held in quantity.
Three practical points regardless of choice:
- Consistency is required. You cannot switch method to suit a given year’s results. Changes need justification and disclosure, and in some jurisdictions tax authority approval.
- Apply it per category, not per transaction. Different methods for different product groups is acceptable where justified; different methods for the same goods is not.
- Check what your system is actually doing. Most WMS and ERP platforms hold a costing method set during implementation and never revisited. Mismatches between the system and what the accounts assume are common and usually surface during an audit.
Lower of cost and net realisable value
One rule sits above all four methods and is frequently overlooked.
Under both IFRS and US GAAP, inventory is carried at the lower of cost and net realisable value — net realisable value being what you could sell it for, less the costs of selling it. If stock has become damaged, obsolete or simply unsellable at its original price, it must be written down regardless of what it cost.
This matters more than it sounds. A valuation method tells you the cost figure; this rule can override it. Operations carrying ageing stock at full cost because the valuation method says so are overstating both their assets and their profit, and an auditor will eventually say so.
It is also the reason a stock ageing report should be run separately from valuation. Under FIFO, old stock carries old costs, which makes it look cheaper to write off than it is to replace — and that can disguise how much dead inventory is sitting on the balance sheet at a value nobody would pay.
What goes into “cost”
Before choosing a method, it is worth being clear what cost actually means, because the purchase price is only part of it and getting this wrong misstates every figure downstream.
Under both IFRS and US GAAP, the cost of inventory includes the costs of bringing the goods to their present location and condition:
- Purchase price, less trade discounts and rebates.
- Import duties and non-recoverable taxes.
- Inbound freight and insurance — the cost of getting goods to you.
- Handling costs directly attributable to acquisition.
- Conversion costs for manufactured goods: direct labour and an allocation of production overhead.
What is excluded matters just as much:
- Outbound freight — a selling cost, not an inventory cost.
- Storage costs, unless storage is a necessary part of the production process.
- Administrative overhead not related to bringing goods to their present condition.
- Selling costs of any kind.
- Abnormal waste — normal wastage is absorbed into cost; an unusual spoilage event is expensed.
The practical consequence is that landed cost, not invoice price, is what should be feeding your valuation. Operations that value stock at supplier invoice price alone understate their inventory asset and overstate their gross margin, sometimes by a substantial amount where goods are imported and freight is significant.
This is also why unit cost changes when freight rates move even though the supplier price has not. A container rate doubling raises the landed cost of everything in that container, and a valuation that ignores it will show margins that do not match the bank balance.
Valuation vs stock rotation — don’t confuse them
FIFO as a valuation method does not mean anyone picks the oldest box. The system will happily charge oldest-cost-first whilst the team picks whatever is nearest.
Physical rotation is a separate discipline driven by spoilage and obsolescence, and it is enforced by layout — flow racking, directed picking, clear date labelling — rather than by whatever your accountant has selected.
Most operations run FIFO physically because perishable goods require it, and FIFO in the accounts because it is permitted everywhere. That they match is convenient rather than necessary. The two decisions are made by different people for different reasons, and confusing them is how a warehouse ends up believing a system setting controls what happens on the shelf.
Why the choice matters beyond the accounts
The valuation method is filed under finance, and it quietly affects several things operations people care about.
Reported margin by product. The cost charged against a sale is what your margin reports are built on. Under weighted average, a product’s margin shifts every time a differently priced delivery arrives, even though nothing about the product or its selling price changed. Under FIFO, margin lags the market — you are selling at today’s prices against costs from a previous purchase, which flatters margin when input costs are rising and understates it when they are falling.
Pricing decisions. If pricing is set from cost plus a percentage, the valuation method is feeding that calculation. A business pricing from FIFO cost during a period of rising input prices is systematically under-pricing relative to replacement cost, and the shortfall only becomes visible when the next purchase order arrives.
Stock write-off decisions. Under FIFO, old stock carries old costs, so writing it off looks cheap. That can encourage holding obsolete inventory rather than clearing it, because the paper loss understates the real cost of the space and capital it occupies.
Borrowing and covenants. Inventory is often part of an asset-based lending calculation. The valuation method changes the reported figure, and in a business with substantial stock the difference between methods can be material to headroom.
Comparability. Benchmarking gross margin against competitors on a different method compares two different things. This catches people out when a US competitor on LIFO appears to have thinner margins than an IFRS-reporting business that is actually less profitable.
None of this argues for one method over another. It argues for knowing which one you are on, checking that the system agrees with the accounts, and remembering that a margin report is the product of an accounting choice as much as of commercial performance.
Where to go deeper
- FIFO vs LIFO — the two compared in detail with the jurisdictional rules.
- What is FIFO — including physical rotation.
- What is LIFO — and the liquidation trap.
- Carrying cost of inventory — what holding stock costs beyond its purchase price.
- What is a stocktake — verifying the quantity the valuation is applied to.
- What is inventory turnover — how quickly the value moves.
The one-line takeaway
Inventory valuation decides which cost is charged against each sale — FIFO, LIFO, weighted average and specific identification give different profit and balance sheet figures from identical stock, and for most of the world LIFO is prohibited, so the real choice is FIFO or weighted average.
Frequently asked questions
What are the main inventory valuation methods? FIFO, LIFO, weighted average cost and specific identification. Retailers with large ranges may also use the retail method, which estimates cost from selling value using a cost-to-retail ratio rather than tracking cost per line.
Which inventory valuation method is best? There is no universal best, and for most businesses the reporting standard narrows it to two. FIFO gives a closing stock value close to replacement cost and is permitted everywhere. Weighted average is simpler for interchangeable goods and smooths price volatility. LIFO can defer tax in inflationary periods but is only available under US GAAP and comes with the conformity rule attached.
Is LIFO allowed under IFRS? No. LIFO is prohibited under IFRS, which is used in most countries. It remains permitted under US GAAP, subject to the conformity rule.
What is weighted average cost? A method where all purchases form a pool and every unit sold is charged the running average cost, recalculated each time a new delivery arrives. It smooths price fluctuations and avoids tracking individual cost layers, which suits interchangeable goods, and it is permitted under both IFRS and US GAAP.
Can I change inventory valuation methods? Not casually. Consistency is a fundamental accounting principle, so you cannot switch method to suit a particular year’s results. A genuine change requires justification, disclosure in the accounts, and usually restatement of comparatives. In some jurisdictions, moving away from LIFO needs tax authority approval and can trigger a significant one-off charge as deferred reserves unwind.
Does the valuation method affect how much tax I pay? Over the whole life of a business, no — the same costs pass through the accounts eventually. What changes is timing. In an inflationary period LIFO defers tax into later years, which improves cash flow now, and that deferral can reverse sharply through LIFO liquidation if stock levels fall in a subsequent year.
What is the retail inventory method? An approximation used by retailers with large, fast-changing ranges. Stock is counted at selling price and converted to cost using a cost-to-retail ratio. It avoids tracking cost per line across thousands of items, at the price of being an estimate rather than an exact figure, and it becomes unreliable where margins vary widely across the range.
How do freight and duty affect inventory value? They form part of the cost. Inventory should be valued at landed cost — purchase price plus inbound freight, duty and non-recoverable taxes — not at supplier invoice price alone. Valuing at invoice price understates the inventory asset and overstates gross margin, which is significant for imported goods.
Does my valuation method control stock rotation? No. Valuation determines which cost is charged against a sale. Physical rotation determines which unit is picked, and is enforced by warehouse layout and process. They are independent decisions that happen to align in most operations.
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