Inventory Adjustments and Unit Cost Accuracy

When you post an inventory adjustment in Luminous and enter a unit cost, how that cost is applied depends on your account's costing method.

FIFO accounts

Positive adjustment with a unit cost entered: Luminous creates a new, dedicated cost layer at the cost you typed. The entered cost is preserved exactly and kept separate from older layers that carry a different cost.

Positive adjustment with no cost entered (blank or zero): The quantity is added to the oldest existing layer and that layer's unit cost is not changed. No cost dilution occurs.

What changed: Before this fix, every positive adjustment — priced or not — was merged into the oldest open layer, silently discarding whatever unit cost you had entered. On-hand value stayed at the old layer's cost even when the adjustment carried a different one.

Weighted-average (WAC) accounts

Positive adjustment with a unit cost entered: Luminous recalculates the running weighted average across existing remaining stock and the incoming units:

new unit cost = (existing remaining qty × existing unit cost + incoming qty × entered cost)
                ÷ new total remaining qty

The cost layer's unit cost and total cost are both updated in place.

Positive adjustment with no cost entered: Only the quantity is updated. The existing unit cost is not diluted by a zero, so your valuation is not marked down.

What changed: Before this fix, the new layer's total cost was calculated as unit cost × unit cost (squaring the cost) rather than unit cost × quantity, producing incorrect valuations whenever a WAC layer was created from scratch by an adjustment.

Editing an adjustment after posting

If you edit an existing adjustment line and supply a unit cost, that cost is now preserved in the cost layer record. Previously, any edit reset the recorded cost to zero.

What to do if you see incorrect past valuations

Adjustments posted before this fix was enabled on your account may carry the old (incorrect) cost calculation. If your on-hand value does not match what you expect for a SKU that received an adjustment with an entered cost, contact support — a cost-layer review or rebuild may be appropriate.

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