Verify the CostingMethod: First, confirm that the product's CostingMethod is set to Average Costing on the Product Type.
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Inspect the Inventory Table: Navigate to the inventory table for the specific product. The AvgLaidInCost field in this table reflects the system's calculated average cost. Compare this value to the laid-in cost shown on the invoice.
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Review the Purchase Transactions: Examine the purchase transactions (PurchaseTrans) associated with the product. The system calculates the average laid-in cost based on the total value of all remaining inventory layers (Total FIFO Value) divided by the total remaining on-hand quantity (Sum (On Hand Remaining)). If recent edits to old production orders (PdOs) have restored inventory from older layers, this may be affecting the average cost.
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Manually Adjust the Costing: If an incorrect cost layer is identified, use the FIFO Adjustment tool to correct it. Since the product is on average costing, the system will not automatically generate the adjustment invoice.
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Create a Manual Invoice: After performing the FIFO adjustment, a "Pending FIFO Adjustment" will appear in the Inventory Valuation report. You must manually create a FIFO adjustment invoice to finalize the cost correction.

CostingMethod: A product configuration field that determines how the system calculates the laid-in cost of an item. The options are FIFO, StandardCost, and Average Costing.
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LaidInCost: The total cost of a product, including the purchase price and any additional fees, such as freight or duties.
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AvgLaidInCost: The weighted average cost of a product, calculated by dividing the total value of remaining inventory by the total remaining on-hand quantity.
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FIFO (First-In, First-Out): An inventory accounting method where the first items purchased are the first ones sold or used.
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Production Order (PdO): A document used to manage the manufacturing process of a product.
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PurchaseTrans: The database table containing all purchase transactions, including LaidInCost data for individual inventory layers.
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FIFO Adjustment Tool: A utility used to manually adjust the cost of specific inventory layers when there are discrepancies.

Avoid Editing Old Production Orders: Modifying old production orders can unpredictably restore inventory from outdated layers, which can distort the average laid-in cost and lead to incorrect accounting.
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Regularly Review Inventory Valuation: Periodically check the Inventory Valuation report for any "Pending FIFO Adjustment" entries to ensure that all manual adjustments are finalized in a timely manner.
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Understand Costing Methods: Be familiar with the differences between FIFO (First-In, First-Out) and Average Costing to anticipate how the system will handle inventory and cost calculations.