If you want Salesforce to automatically generate a unique number or ID for records, such as CASE-0001, OPP-00023, or REQ-000100, you can use an Auto Number field.
An Auto Number field is one of the most useful field types in Salesforce because Salesforce automatically creates a unique value for every new record.
You don’t need to write Apex code, create a Flow, or use formulas. You just configure the field once, and Salesforce handles the numbering automatically.
In this tutorial, I’ll show you how to create an Auto Number field from scratch in Salesforce Lightning Experience, explain what each setting means, and share some useful tips to help you configure it correctly the first time.