# Understand Inventory and Serial Number Reservation

**Navigation:** Register → Layaway.

Serialized merchandise needs special care because each physical unit has its own serial number or IMEI.

- **Locked serial:** Use this when a specific unit should remain committed to the layaway.
- **Editable serial:** Use this for flexible fulfillment, preorders, or prepaid sales when the final unit will be chosen later.

Before delivery, confirm that every serialized quantity has a valid serial number. If multiple units are required, enter every required serial as prompted. Never promise a specific unit unless it is actually reserved.