Build LIFO layers and a qualified comparison

Compute periodic and perpetual LIFO, bridge LIFO to FIFO with a dated reserve, and identify margin effects when older layers liquidate.

Updated Sep 10, 2026 Review due Nov 8, 2026

Cedar Trail's second purchase happens after its first sale. A periodic LIFO schedule treats that late layer as available to the period's total cost assignment. A perpetual schedule cannot send that cost to an earlier sale.

Compute both timelines

Periodic LIFO assigns 80 units at $14, 60 at $12, and 30 at $10 to 170 units sold. Cost of goods sold is $2,140; ending inventory is 70 units at $10, or $700.

Perpetual LIFO assigns the first 120-unit sale 60 at $12 and 60 at $10. The second sale removes 50 at $14. Cost of goods sold is $2,020; ending inventory is 40 units at $10 plus 30 at $14, or $400 + $420 = $820. Both reconcile to $2,840 available.

LIFO is a cost-flow assumption, not a claim that Cedar Trail physically shipped its newest units. US GAAP permits it within applicable scope, while tax rules can constrain whether and how an entity uses it for book reporting. This module does not teach tax qualification; retain it as a separate current-research question.

IFRS comparison

US GAAP: LIFO is permitted within its applicable scope.

IFRS: IAS 2 does not permit LIFO for interchangeable inventory.

Effect: An IFRS reporter must use another permitted cost formula and recompute the inventory amounts. Removing the LIFO label does not convert the US-GAAP figures.

Use the reserve as a bridge, not a verdict

Periodic FIFO ending inventory is $980 and periodic LIFO ending inventory $700. The $280 difference is a bounded LIFO reserve only if the date, units, pool, currency, and comparison basis match. The change in reserve, not the ending reserve, bridges period cost of goods sold. Tax effects and disclosed scope stay separate.

Watch for liquidation

If current additions fall below removals, LIFO can reach an older, lower-cost layer. Gross profit may rise because old cost enters current expense. Trace the depleted quantity and old-versus-current cost effect before attributing margin to pricing, demand, productivity, or management skill.

Use a separate stipulated pool: current cost is $14 per unit, but a 20-unit quantity decline releases a layer carried at $8 per unit. Cost of goods sold is $120 lower than assigning current cost, 20 × ($14 − $8), so pretax income is $120 higher before tax. That is a method-and-quantity effect, not cash and not evidence that selling price or operations improved. This liquidation pool is independent of Cedar Trail's 240-unit method-comparison stream.

Prepare a reviewer note with opening layers, additions, removals, liquidated layers, reserve movement, tax and disclosure references, operating explanation, and unanswered facts. “Margin improved” is not a release conclusion.

Follow the focused learning path

Start with the Cedar LIFO, reserve, and liquidation example. Then complete the Northstar review with a different event stream and liquidation fact pattern. Return to the larger Cedar Trail example when comparing every inventory method.