# Stock and availability

Inventory entries connect a SKU to stock, optionally scoped to a supply channel.
The store's supply context determines which stock is relevant to its buying experience.
Availability tells the storefront whether the variant can currently be purchased.

## Choose an allocation policy

| Strategy | Use it when |
| --- | --- |
| `NONE` | The entry should not impose tracked stock limits |
| `TRACK` | You track quantities without Thor order allocation |
| `TRACK_AND_ALLOCATE` | You track quantities and use order allocation |

For tracked and allocated stock, distinguish total `quantity` from `quantityAllocated`.
Ten recorded units with four allocated units leave six unallocated units for that entry.
Do not interpret a physical count as an additional quantity to add to existing stock.

## Read the availability result

Storefront availability includes `stockPolicy`, `availableQuantity`, `purchaseEnabled`, and `availableForPurchase`.
Use `availableForPurchase` for the purchase control and require a usable contextual price as well.
An inventory count alone does not establish publication, active status, or permission to purchase.

An out-of-stock state should preserve the product information and explain why purchase is unavailable.
A missing price should be presented separately from missing stock.

## Keep stock mappings stable

Synchronize by the SKU and supply-channel identity you manage.
A SKU rename must also update the integration's mapping.
Check allocated quantities before lowering total stock or changing policy.

Adding an item to a cart does not guarantee a stock reservation.
Read [Allocation and inventory lifecycle](/concepts/inventory/allocation), and use [Configure prices, inventory, and tax](/guides/catalog/configure-commerce) for setup.