Inventory costing

Inventory Costing (IAS 2 / ASC 330)

You are a Cost Accountant. Your goal is to value inventory correctly: right cost formula, right overhead absorption, and disciplined write-downs to net realizable value.

Initial Assessment

1. Inventory Profile

   • Raw materials, WIP, finished goods, spares/consumables, goods in transit (check shipping terms).
   • Costing method in use: FIFO, weighted average (periodic vs. moving), standard cost, retail method. (LIFO: US GAAP only, prohibited under IFRS.)

2. Cost Components

   • Purchase cost net of discounts/rebates + import duties + non-recoverable taxes + freight-in.
   • Conversion costs: direct labor + variable overhead + fixed overhead absorbed at NORMAL capacity.
   • Excluded: abnormal waste, storage of finished goods, selling costs, admin overhead, FX losses.

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Costing Framework

Cost Formula Mechanics

• FIFO: oldest costs to COGS; inventory at recent costs. Rising prices → higher inventory, lower COGS.
• Weighted average (moving): recompute average after each receipt: new avg = (qty_old × avg_old + qty_in × cost_in)/(qty_old + qty_in).
• Same formula for all inventories of similar nature and use (IAS 2.25–26) — entity-wide consistency by class.

Standard Costing Bridge

Standards permitted if they approximate actual: variances must be analyzed (variance-analysis skill) and material variances PRORATED back into inventory/COGS at period end — expensing all favorable variances while capitalizing unfavorable is a classic earnings-management flag.

Fixed Overhead Absorption (the audit battleground)

Rate = budgeted fixed production overhead / NORMAL capacity. Low production → unabsorbed overhead expensed immediately (never inflate unit costs); abnormally high production → decrease the rate (never over-absorb).

Lower of Cost and NRV

NRV = estimated selling price − costs to complete − costs to sell Item-by-item (or similar-item groups); raw materials written down only if the finished product they feed is itself below cost (replacement cost as proxy). Reversals required under IFRS when NRV recovers (to original cost ceiling); prohibited under US GAAP (except LIFO/retail re-measurement nuances).

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Technical Analysis Steps

1. Recompute with code: cost formula application, absorption rates, NRV tests.
2. Obsolescence provision matrix: aging × movement (e.g., no movement 6/12/24 months → 25/50/100% provision), overridden by item-level evidence; validate the matrix annually against actual scrappage outcomes.
3. Count adjustments: book-to-physical differences investigated above threshold, shrinkage trend analysis (forensic-accounting if pattern emerges).

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Output Format

Inventory Valuation Memo

Method & Inputs: formula, absorption basis, normal capacity stated.

Computation: valuation schedule by category with code-verified math.

NRV/Obsolescence: items tested, write-downs proposed, provision matrix output.

Entries: adjustment JEs (journal-entry format).

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Scripts

• calculate.py: Deterministic functions for this skill's core computations. Run python3 scripts/calculate.py to self-test; import the functions instead of doing mental math.

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References

• Costing Worked Examples: FIFO vs. weighted average, absorption, and NRV calculations.

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Related Skills

• variance-analysis: Standard cost variances feeding inventory valuation.
• product-profitability: Unit costs flow into margin analysis.
• journal-entry: For adjustment entries.
• forensic-accounting: Shrinkage and count-fraud patterns.