The same units may move while cost of sales and closing inventory differ under different cost formulas. The policy must be clear before opening balances are loaded, and the team should distinguish quantity movement from value calculation.
Do not switch methods to flatter a month
A business purchases 100 units at SAR 10, then 100 at SAR 14, and sells 120 units. Ignoring additional costs, total cost is SAR 2,400. FIFO assigns SAR 1,000 + SAR 280 = SAR 1,280 to sales and leaves SAR 1,120 in inventory. Periodic weighted average gives SAR 12 per unit, SAR 1,440 for sales and SAR 960 for ending inventory.
Both methods leave eighty units. The difference comes from allocating cost between goods sold and goods retained. Keep quantities, period and cost inputs identical when comparing formulas. A moving average also depends on receipt and issue timing, so it is not automatically the same as an average calculated over the whole month.
Incorrect movements can undermine a sound valuation policy. A sale entered before its receipt may create negative stock, and late freight invoices may affect a batch already partly sold. Establish how the system handles these events and how subsequent cost changes affect sales and remaining inventory. Test the result against a small sample you can calculate independently.
If inventory valuation differs from the general ledger, check matching dates, posting status and inclusion of cost adjustments. Changing valuation methods will not fix a discrepancy caused by an incomplete import or an unposted document.
The same quantity, a different cost
IAS 2 addresses formulas such as first-in first-out and weighted average for interchangeable items, and specific identification for particular items. Inventory is also measured at the lower of cost and net realisable value under the applicable requirements.
Two batches reveal the effect
With rising purchase prices between the two batches, FIFO assigns the earlier, lower costs to sales first in this example, while the average blends both batches. Gross profit and ending inventory therefore differ despite an unchanged total cost of available units. Do not automatically interpret a higher monthly margin as better pricing without examining cost allocation and batch movements.
Data needed before comparing methods
- Classify items and whether they are interchangeable.
- Document cost components and calculation formula.
- Test purchases at different prices, then a sale and reversal.
- Reconcile value to the ledger and review write-downs where needed.
Connect the choice to the item
Interchangeable items with similar uses need a consistent policy appropriate to the reporting framework. A specific machine identified by serial number and bought for a particular customer may be better understood through its identified cost than an average combining different units. A barcode alone does not make inventory economically unique; the nature and interchangeability of the goods matter.
When presenting product margin, state whether purchasing-related charges and adjustments are complete. An early margin based only on the supplier invoice may fall when freight arrives. Treat the first figure as provisional and distinguish it from the settled batch cost.
Sources & further reading
Visit the original source to explore the concept and its wider context.
General educational content. Appropriate treatment depends on your business and accounting policies; consult your accounting professional when applying it to business records.
