Defining General Settings for Serial Numbers 
You can define serial numbers for all of the items in inventory or you can define serial numbers for specific items. For more information about creating serial numbers for specific items only, see Defining Serial Number Settings per Item.
Note
The settings defined per item in the Item Master Data window override the settings defined in the General Settings window.
During the creation of serial number-managed items you can do the following:
Specify the default method for managing serial numbers.
Specify whether serial numbers are created automatically on receipt of items.
Specify the method for managing unique serial numbers in SAP Business One.
Note
Items managed by serial and batch numbers must be inventory items (they cannot be only sales items or purchase items). Therefore, the selected item cannot be defined as a phantom item.
Procedure
Choose
Administration 
System Initialization General Settings Inventory tab Items 
tab.Specify the following data:
Management Method
Unique Serial Numbers by (optional)
Auto. Create Customer Equipment Card (optional)
Automatic Serial Number Creation on Receipt (optional)
NoteThis option is only displayed, if you select the On Release Only option. For more information, see Creating, Updating, and Deleting Customer Equipment Cards.
End of the note.
To save the data, choose the Update button and the OK button.