Use stage validation to control when a case enters your stage.
For example, you can check if an Auto Loan has a credit score attached to it before sending the case to a finance manager for approval. By defining the entrance criteria for a stage, you set expectations for users and guide them to successful case resolution.
The following validation techniques are supported:
A validation rule
A list of attachment categories
A when condition
This method is not supported by the last stage in the sequence.
Stage validation techniques are not mutually exclusive. You can use some, all, or none of them, based on your requirements.