Sample Validation Rule:
AND(
Is_Active__c,
NOT( ISCHANGED( Is_Active__c ) ),
NOT(ISNEW())
)Output:
How to lock record from editing when a check box is set to true in Salesforce?
Sample Validation Rule:
AND(
Is_Active__c,
NOT( ISCHANGED( Is_Active__c ) ),
NOT(ISNEW())
)Output: