Inventories and Cost of Sales

Introduction and context

Inventory is often the largest current asset of a trading or manufacturing entity. Its measurement affects reported profit, tax assessments, liquidity indicators, borrowing capacity, management bonuses and decisions about purchasing and pricing. Unlike cash, inventory does not normally generate income until it is sold; therefore, financial reporting must determine both the amount remaining as an asset and the amount transferred to cost of sales.

The central accounting problem is one of allocation. The total cost of goods available for sale must be allocated between closing inventory and cost of sales. That allocation requires reliable recognition of inventory, an appropriate cost formula, careful assessment of recoverability, and adequate disclosure.

This chapter is based primarily on IAS 2 Inventories, as issued by the International Accounting Standards Board. Entities applying US GAAP or a jurisdictional standard should confirm local requirements, particularly regarding permitted cost formulas, last-in-first-out accounting and reversals of write-downs.

Learning objectives

By the end of this chapter, the reader should be able to:

1. Define inventory and determine when it should be recognised.
2. Distinguish product costs from period costs and calculate inventory cost.
3. Apply specific identification, FIFO and weighted-average cost formulas.
4. Measure inventory at the lower of cost and net realisable value (NRV).
5. Account for write-downs, reversals, losses and abnormal waste.
6. Apply retail and gross-profit estimation methods appropriately.
7. Analyse effects on profit, tax, working capital and performance indicators.
8. Evaluate disclosure, governance, technology and ethical issues relating to inventory.

1. The nature and scope of inventory

Inventory comprises assets:

• held for sale in the ordinary course of business;
• in the process of production for such sale; or
• in the form of materials or supplies to be consumed in production or in rendering services.

Thus, inventory includes merchandise held by a retailer, finished goods, work in progress, raw materials, packaging materials and production supplies. Spare parts may be inventory if they are consumed in production; major stand-by equipment may instead be accounted for as property, plant and equipment when it meets the relevant recognition criteria.

Inventory is normally a current asset because it is expected to be sold or consumed in the entity’s normal operating cycle. The operating cycle may exceed twelve months in industries such as construction, shipbuilding and wine production. Classification should reflect the operating cycle rather than an arbitrary twelve-month rule.

The accounting process can be represented as follows:

Figure: Allocation of the cost of goods available for sale between cost of sales and closing inventory.

For a trading entity, the basic reconciliation is:

These equations assume a periodic inventory framework and that the relevant amounts are measured using a consistent cost basis. Under a perpetual system, cost of sales is updated whenever a sale occurs, but the allocation principle remains the same.

2. Recognition and measurement of inventory cost

Inventory is recognised when the entity controls the resource, expects future economic benefits and can measure its cost reliably. In practice, purchase terms, delivery conditions, acceptance clauses and consignment arrangements determine whether goods belong to the buyer at the reporting date.

Goods held on consignment generally remain the property of the consignor until sale. Conversely, goods purchased under a delivered-duty-paid arrangement may be recognised by the buyer when delivery and control pass under the contract. Legal title is important evidence but is not always decisive; the substance of the arrangement must be considered.

2.1 Components of cost

The cost of inventory includes:

• purchase price, after trade discounts, rebates and similar deductions;
• import duties and non-refundable taxes;
• transport, handling and other directly attributable acquisition costs;
• costs of conversion, including direct labour and systematic allocation of production overhead; and
• other costs incurred to bring inventory to its present location and condition.

Production overhead includes fixed and variable production costs. Fixed overhead is allocated using normal production capacity, not merely the actual output of an unusually quiet period. When production is abnormally low, the unallocated fixed overhead is recognised as an expense rather than being loaded into inventory. Variable overhead is allocated based on actual use of production facilities, subject to systematic and rational application.

Examples of costs normally excluded from inventory include abnormal waste, storage costs not necessary for a further production stage, administrative overhead unrelated to bringing inventory to its present condition, selling and distribution costs, and interest except where qualifying inventories require a substantial period to get ready for intended sale or use under applicable borrowing-cost requirements.

2.2 Worked example: manufacturing cost

Illustrative Manufacturing Ltd produces 10,000 units. Direct materials are CU120,000, direct labour CU80,000, variable production overhead CU30,000 and fixed production overhead CU60,000. Normal capacity is 12,000 units. Actual production is 10,000 units, and the shortfall is not caused by a normal seasonal pattern.

Eligible production cost before considering abnormal underproduction is CU290,000 (120,000 + 80,000 + 30,000 + 60,000). Fixed overhead allocated at normal capacity is CU5 per unit (CU60,000 ÷ 12,000 units), so CU50,000 is included in production inventory. The remaining CU10,000 is an expense because of abnormal underproduction.

The cost assigned to the 10,000 units is therefore CU280,000, or CU28 per unit. This treatment avoids overstating inventory and deferring the cost of idle capacity to future periods.

3. Cost-flow assumptions and inventory systems

A cost-flow assumption is an accounting convention for assigning accumulated costs to units sold and units remaining. It need not describe the physical movement of goods. A warehouse may physically issue the oldest goods first while the entity uses a weighted-average formula for financial reporting.

3.1 Specific identification

Specific identification assigns the actual cost of each identifiable item to inventory or cost of sales. It is appropriate for items that are not ordinarily interchangeable, such as customised machinery, unique property units, high-value gemstones or specific projects. It is unsuitable when large numbers of interchangeable items are routinely purchased and sold, because management could selectively identify costs and manipulate profit.

3.2 First-in, first-out (FIFO)

FIFO assumes that the earliest costs are assigned to the earliest sales. Closing inventory therefore consists largely of recent costs. During periods of rising prices, FIFO usually produces lower cost of sales, higher closing inventory and higher reported profit than weighted average. The effect reverses or diminishes when prices fall.

3.3 Weighted-average cost

Under a periodic weighted average, one average cost is calculated for all units available during the period:

The formula assumes that units are interchangeable and that a common average is an appropriate representation of cost. Under a perpetual moving-average system, a new average is calculated after each purchase.

3.4 Worked comparison

Assume the following transactions:

Units available are 400 and total cost is CU4,900. Closing units are 150.

Under FIFO, the 250 units sold comprise 100 units at CU10 and 150 units at CU12:

• Cost of sales = CU1,000 + CU1,800 = CU2,800.
• Closing inventory = 50 units at CU12 plus 100 units at CU15 = CU2,100.

Under periodic weighted average:

• Average cost per unit = CU4,900 ÷ 400 = CU12.25.
• Cost of sales = 250 × CU12.25 = CU3,062.50.
• Closing inventory = 150 × CU12.25 = CU1,837.50.

Both methods allocate the same total cost of CU4,900, but they produce different timing of expense recognition. In the rising-price example, FIFO reports higher profit by CU262.50 before tax (CU3,062.50 − CU2,800), assuming revenue and other costs are unchanged.

A cost formula should be applied consistently to inventories having a similar nature and use. A different formula may be justified for inventories with a different nature or use, but changing methods merely to manage profit is inappropriate. Changes in accounting policy must comply with the applicable standard’s requirements.

4. Net realisable value and the lower-of-cost rule

Inventory is measured at the lower of cost and net realisable value. NRV is an entity-specific estimate of the net amount expected to be realised from sale in the ordinary course of business.

The terms in the equation must be measured consistently in the entity’s functional currency and relate to the same unit, product, condition and reporting date. NRV is not necessarily fair value: fair value is a market-participant measurement, whereas NRV reflects the entity’s expected selling process and selling costs.

4.1 Applying the rule

Assume a product has cost of CU50 per unit. Its expected selling price is CU47, completion costs are CU2 and selling costs are CU1 per unit. NRV is CU44. The inventory must be reported at CU44, creating a write-down of CU6 per unit.

If 2,000 units are held:

• Cost = 2,000 × CU50 = CU100,000.
• NRV = 2,000 × CU44 = CU88,000.
• Write-down expense = CU12,000.
• Carrying amount = CU88,000.

The write-down is generally recognised in profit or loss in the period in which the decline occurs. It may be presented within cost of sales or as a separate inventory impairment expense, provided presentation is clear and consistent.

Assessment is normally made item by item. Grouping may be appropriate for similar or related items, but broad offsetting of profitable and loss-making products can conceal impairment. Materials are not written below cost when finished goods in which they will be incorporated are expected to sell at or above cost. If finished goods are impaired, however, the materials may need to be written down to replacement cost or another appropriate measure of recoverability, subject to the applicable reporting framework.

4.2 Reversal of a write-down

At each subsequent reporting date, NRV is reassessed. If circumstances causing the original write-down no longer exist, the write-down is reversed, but only to the amount of the original reduction. The revised carrying amount cannot exceed the cost that would have been recognised had no write-down occurred.

For example, inventory originally costing CU50 was written down to CU44. At the next reporting date, NRV rises to CU48. The entity reverses CU4 per unit, not CU6, and reports the inventory at CU48. A reversal increases profit in the period of reversal.

5. Estimation methods

A complete physical count is not always practical, especially for interim reporting, disaster recovery or retail operations. Estimation methods can be useful, but they are substitutes for detailed records only when their reliability is demonstrated and they are reconciled to physical evidence.

5.1 Retail method

The retail method estimates cost by applying a cost-to-retail percentage to retail selling value. A simplified formula is:

The ratio should reflect consistent treatment of purchases, mark-ups, markdowns, returns and shortages. Under some reporting frameworks, markdowns are excluded from the denominator to avoid anticipating profit, while mark-ups and markdowns may be treated differently depending on the specific retail-method guidance. The entity must therefore apply the relevant standard precisely.

5.2 Gross-profit method

The gross-profit method estimates cost of sales by applying an historical gross-profit rate to sales:

If net sales are CU600,000 and the historical gross-profit rate is 30%, estimated cost of sales is CU420,000 (CU600,000 × 70%). If opening inventory plus purchases is CU500,000, estimated closing inventory is CU80,000.

This method is appropriate only when the gross margin is reasonably stable and there are no major changes in product mix, prices, discounts, shrinkage, theft or market conditions. It is particularly useful after fire, flood or system failure, but it is not a substitute for a physical count in audited annual statements where reliable records can be obtained.

6. Periodic and perpetual inventory systems

A periodic system determines cost of sales after a physical count at the reporting date. Purchases are recorded during the period, and the closing count is used to derive cost of sales. A perpetual system updates quantity and value records continuously, usually through enterprise resource planning (ERP) software and barcode or radio-frequency identification technologies.

Perpetual records improve visibility over stock levels, reorder points and shrinkage. They do not remove the need for physical verification. Differences may arise from theft, damage, incorrect scanning, timing errors, unit-of-measure errors or master-data problems. Adjustments should be investigated, authorised and documented rather than automatically posted.

A robust inventory control environment separates purchasing, receiving, custody, recording and approval. Cycle counts can test high-value or high-risk items more frequently than low-risk items. Cut-off testing around year-end is essential: goods received before year-end should not be omitted from inventory, and goods dispatched before year-end should not remain in closing inventory when control has transferred.

7. Effects on profit, tax and working capital

Inventory measurement affects profit through cost of sales. If closing inventory is overstated, cost of sales is understated and current-period profit is overstated. The reverse occurs when closing inventory is understated. The effect generally reverses in the following period when the inventory is sold, but the timing distortion can affect reported performance, covenants and remuneration.

The relationship is:

An increase of CU10,000 in closing inventory, with all other variables unchanged, reduces current-period cost of sales and increases gross profit by CU10,000. Before tax, operating profit changes by the same amount if no other expense is affected.

Tax consequences depend on local tax law. Accounting write-downs may be deductible immediately, deductible only when realised, or subject to specific evidence requirements. A temporary difference may arise between the accounting carrying amount and tax base, potentially creating deferred tax. Management must not assume that an accounting provision automatically reduces current tax.

Inventory also affects working capital:

A write-down reduces current assets and working capital. However, reducing obsolete stock through sale or disposal may improve inventory turnover and reduce storage costs even though it may initially reduce profit. Useful indicators include:

Average inventory is commonly calculated as (opening inventory + closing inventory) ÷ 2 when those balances reasonably represent the period. These ratios are meaningful only when accounting policies, seasonality, product mix and inflation are considered. A high turnover may indicate efficiency, but it may also signal stock-outs or inadequate safety stock.

8. Applied case: Northstar Electronics Ltd

The following is an illustrative case, not a report on a real entity.

Background

Northstar Electronics sells smart-home devices. At 31 December, its records show 5,000 units of Model X at a cost of CU80 each. The products are complete, but a new model has reduced expected selling prices. Management proposes retaining the inventory at cost because all units were purchased and paid for.

Problem

Expected selling price is CU76 per unit. Packaging and delivery costs necessary to sell the units are CU3 per unit. A customer has also returned 200 units; these are saleable but require inspection costing CU2 per unit. Northstar has not yet recorded the return or the inspection cost. The tax authority allows inventory write-downs only when the goods are sold or destroyed.

Analysis

The returned goods are controlled by Northstar and remain inventory if they meet the recognition criteria. The expected NRV is CU76 − CU3 = CU73 for ordinary units. For returned units, NRV is CU76 − CU3 − CU2 = CU71.

The write-down is:

• 4,800 ordinary units: cost CU384,000; NRV CU350,400; write-down CU33,600.
• 200 returned units: cost CU16,000; NRV CU14,200; write-down CU1,800.
• Total cost: CU400,000; total NRV: CU364,600; total write-down: CU35,400.

Northstar should recognise inventory at CU364,600 and a CU35,400 expense. It should record the customer return appropriately, investigate whether a refund liability or other obligation exists, and document the NRV evidence. Because tax law disallows the deduction until sale or destruction, the accounting write-down may create a deductible temporary difference, subject to recognition criteria for deferred tax.

Outcome and learning points

The proposed cost measurement would overstate assets and current profit by CU35,400 before tax. It would also overstate working capital and understate inventory impairment risk. The case demonstrates that payment and historical cost do not guarantee recoverability; NRV must be reassessed at each reporting date. It also shows why returns, selling costs, tax rules and product-specific evidence must be integrated into the closing process.

9. Disclosure, governance and professional judgement

Financial statements should disclose, where material:

• the accounting policies used to measure inventories, including the cost formula;
• the total carrying amount and relevant classifications such as merchandise, materials, work in progress and finished goods;
• inventory recognised as an expense during the period;
• write-downs and reversals of write-downs;
• circumstances or events leading to reversals; and
• inventory pledged as security for liabilities.

Entities should also explain significant estimation uncertainty where NRV, obsolescence, forecast selling prices or completion costs are highly judgemental. Consistency does not mean blindly repeating last year’s assumptions. It means applying a coherent policy while updating estimates for current evidence.

Governance risks include deliberate overstatement of quantities, delaying write-downs, recording fictitious goods received, manipulating cut-off, classifying selling costs as production costs and using optimistic forecasts to avoid impairment. Ethical professional behaviour requires evidence-based estimates, challenge by finance leadership, independent review of unusual movements and transparent communication with auditors, lenders and investors.

10. Technology and contemporary developments

ERP systems can connect purchase orders, goods receipts, warehouse movements, sales invoices and general-ledger postings. Barcode scanning, RFID, drones and computer vision can improve count completeness and reduce manual errors. Predictive analytics can identify slow-moving items by combining age, demand, returns and margin data.

Artificial intelligence may assist with demand forecasting and anomaly detection, but it does not replace management’s responsibility for NRV. Models can reproduce biased historical demand, fail during structural market changes or treat promotional sales as sustainable demand. Controls should include approved data sources, versioned models, human review, explainable exception reports, access restrictions and post-implementation validation.

Contemporary supply chains also raise sustainability and resilience issues. Excess inventory can represent wasted materials, energy and packaging, while insufficient inventory may increase expedited transport and service failures. Financial reporting remains governed by applicable accounting standards, but inventory governance should connect valuation, climate-related disruption, supplier concentration and obsolescence planning.

11. Limitations and best-practice framework

No cost formula perfectly represents economic consumption in every market. FIFO and weighted average may produce materially different results during inflation. NRV estimates are sensitive to demand forecasts and selling costs. Gross-profit estimates become unreliable when margins change. Perpetual systems can create false confidence if master data and physical controls are weak.

Best practice includes:

1. Define ownership and cut-off rules contractually and operationally.
2. Maintain item-level records with unit, location, age and cost information.
3. Select cost formulas based on the nature and use of inventory, not desired profit.
4. Reconcile perpetual records to cycle counts and year-end physical counts.
5. Review ageing, damage, returns, cancellations and forecast demand for NRV indicators.
6. Separate normal production costs from abnormal waste, idle capacity and selling costs.
7. Document assumptions, evidence, approvals and subsequent-sale results.
8. Reconcile accounting carrying amounts to tax bases and assess deferred tax.
9. Analyse turnover and working capital together with service-level and stock-out data.
10. Disclose material policies, judgements, write-downs and pledged inventory clearly.

Chapter Summary

Inventory accounting allocates the cost of goods available for sale between cost of sales and closing inventory. Inventory cost includes purchase and conversion costs required to bring goods to their present location and condition, while abnormal waste, unnecessary storage, selling costs and unrelated administration are generally excluded. Specific identification is suited to unique items; FIFO and weighted average are used for interchangeable items and may produce different profit and asset amounts during changing prices.

Inventory is measured at the lower of cost and NRV. NRV equals estimated selling price less completion and selling costs. Write-downs reduce profit and working capital, while permitted reversals increase profit but cannot raise inventory above its original cost. Retail and gross-profit methods provide estimates when detailed records are unavailable, but they require stable assumptions and independent validation.

Inventory choices affect profit, tax timing, deferred tax, liquidity ratios, turnover and contractual performance. Effective governance requires physical verification, cut-off controls, reliable systems, evidence-based estimates and transparent disclosure. Technology can improve visibility and forecasting, but professional judgement and accountability remain essential.

Key Terms

Inventory: Assets held for sale, in production for sale, or consumed in production or service delivery.

Cost of sales: The cost assigned to inventory sold during the reporting period.

Cost formula: A method for assigning accumulated inventory costs between units sold and units remaining.

Specific identification: Assignment of the actual cost of an identifiable item to that item.

FIFO: First-in, first-out assumption that earliest costs are assigned to earliest sales.

Weighted average: A cost formula using total cost divided by total units available.

Periodic inventory system: A system in which cost of sales is determined after a physical count or period-end computation.

Perpetual inventory system: A system that updates inventory records and usually cost of sales continuously.

Net realisable value: Expected selling price less completion and selling costs.

Write-down: Reduction of inventory carrying amount when cost exceeds NRV.

Reversal: Recovery of a previous inventory write-down, limited to the original cost.

Conversion cost: Direct labour and systematically allocated production overhead.

Normal capacity: Expected average production over a normal range of periods.

Abnormal waste: Unusual or avoidable material, labour or production loss expensed rather than included in inventory.

Retail method: Estimation of inventory cost by applying a cost-to-retail ratio.

Gross-profit method: Estimation method using an expected gross-profit rate to derive cost of sales.

Inventory turnover: Cost of sales divided by average inventory.

Working capital: Current assets less current liabilities.

Cut-off: Correct assignment of purchases and sales to the reporting period in which control transfers.

Temporary difference: Difference between an asset or liability’s accounting carrying amount and its tax base.

Review Questions

Short Answer Questions

1. What three categories of assets meet the definition of inventory?
2. Why is abnormal underproduction not normally included in inventory cost?
3. State the formula for net realisable value.
4. What is the principal difference between a periodic and a perpetual inventory system?
5. Why can a write-down of inventory create a deferred tax difference?

Long Answer Questions

1. Explain the components of inventory cost for a manufacturing entity and distinguish includable production costs from excluded costs.
2. Compare specific identification, FIFO and weighted-average cost formulas, including their effects during rising prices.
3. Explain the lower-of-cost-and-NRV requirement and the accounting treatment of subsequent reversals.
4. Evaluate the reliability and limitations of the retail and gross-profit estimation methods.
5. Discuss how inventory measurement influences profit, tax, working capital, ratios and management behaviour.

Analytical / Application Questions

1. A retailer has 600 units costing CU20 each and 400 units costing CU26 each. It sells 700 units. Calculate cost of sales and closing inventory under FIFO and periodic weighted average, then interpret the difference if prices are rising.
2. A manufacturer holds 3,000 units costing CU42 each. Expected selling price is CU40, completion cost is CU1.50 and selling cost is CU0.75 per unit. Determine NRV, the required write-down and the carrying amount. Explain two pieces of evidence management should obtain.
3. An entity’s closing inventory is overstated by CU75,000 because obsolete goods were not written down. Analyse the immediate effects on cost of sales, profit, current assets and working capital, and explain why the tax effect cannot be determined without reference to local tax law.

Multiple Choice Questions with Answers

Question 1

Which item is normally included in the cost of inventory?

A. Abnormal production waste

B. Selling and distribution costs

C. Direct labour used in production

D. General administrative costs unrelated to production

Correct Answer: C. Direct labour used in production

Question 2

Under FIFO during a period of rising prices, which outcome is generally expected compared with weighted average?

A. Higher cost of sales and lower profit

B. Lower cost of sales and higher closing inventory

C. Identical cost of sales and identical closing inventory

D. Lower revenue and higher tax expense

Correct Answer: B. Lower cost of sales and higher closing inventory

Question 3

An item costs CU30, has an estimated selling price of CU28, completion costs of CU2 and selling costs of CU1. What is its NRV?

A. CU25

B. CU26

C. CU28

D. CU31

Correct Answer: A. CU25

Question 4

If inventory cost is CU100,000 and NRV is CU92,000, what amount is normally recognised as the write-down?

A. CU92,000

B. CU100,000

C. CU8,000

D. CU192,000

Correct Answer: C. CU8,000

Question 5

Which inventory is most suitable for specific identification?

A. Thousands of identical grocery items

B. Interchangeable bolts purchased in bulk

C. Unique customised machinery held for a named customer

D. Standardised fuel products

Correct Answer: C. Unique customised machinery held for a named customer

Question 6

Total cost of goods available is CU60,000 and total units available are 5,000. What is periodic weighted-average cost per unit?

A. CU8

B. CU10

C. CU12

D. CU15

Correct Answer: C. CU12

Question 7

A permitted reversal of an inventory write-down may increase inventory to:

A. Any amount management considers prudent

B. Fair value without restriction

C. An amount not exceeding the original cost

D. Zero only

Correct Answer: C. An amount not exceeding the original cost

Question 8

Which formula estimates closing inventory using the gross-profit method?

A. Opening inventory + purchases − estimated cost of sales

B. Sales − purchases + opening liabilities

C. NRV − completion costs − selling costs

D. Cost of sales ÷ revenue × 365

Correct Answer: A. Opening inventory + purchases − estimated cost of sales

Question 9

If closing inventory is overstated and all other figures remain unchanged, current-period cost of sales is:

A. Overstated

B. Understated

C. Unaffected in every system

D. Equal to revenue

Correct Answer: B. Understated

Question 10

Which control most directly helps detect inventory cut-off errors?

A. Comparing the year-end goods-received notes with purchase invoices

B. Increasing the selling price of slow-moving goods

C. Using only historical gross margins

D. Removing all damaged goods from the count without documentation

Correct Answer: A. Comparing the year-end goods-received notes with purchase invoices