On-hand, demand and ATP

Inventory balances are projections from events. Operators use them for the current answer; the ledger remains the audit trail.

item x locationavailable-only useplanning projection

The four numbers

Number	Meaning
On hand	Sum of all lot balances — every disposition. Scrap and consumption reduce it; receipts and gains increase it.
Demand	Quantity promised to downstream work, such as sales or manufacturing ingredients.
Expected	Quantity expected to arrive or be produced, but not yet physical on-hand stock.
Available to promise	Available stock + expected supply − demand.

On-hand vs usable

Lot balances are split by disposition: available, blocked, and rejected. Only available quantity is usable for selling, consuming, and stocktake reconciliation. Blocked and rejected quantity remains on the lot for traceability, but it is intentionally held back from normal use.

How balances change

Action	Balance effect
Receive a purchase order	Increases on hand and releases matching expected supply.
Order a purchase order	Increases expected supply until receipt or release.
Ship or consume stock	Decreases on hand and releases matching demand when applicable.
Create or adjust demand	Increases or releases demand without moving physical stock.
Complete a stocktake	Posts gains, losses, or verification and updates last verified date.
Scrap stock	Decreases on hand from the scrapped disposition.

Default-location planning constraint

The code keeps balances per location. Some planning projections are default-location pinned in v1, while physical operations such as receive, adjust, stocktake, and transfer can resolve or select a location depending on the workflow.