Creating a mandatory Reason Lost field for lost opportunities using a validation rule

In this recipe, we will create a validation rule that ensures that an explanation is provided whenever an opportunity is set to Lost.

To store the reason for the lost opportunity, we will create a custom field called Reason Lost (which we will name Reason_Lost__c). This will be created and checked using a validation rule.

Getting ready

Carry out the following steps to create a custom Reason Lost field on the opportunity object:

1. Click on the Setup gear icon in the top right-hand corner of the main Home page, as shown in the following screenshot:

2. Click the Setup option, as shown in the following screenshot:

3. Navigate to the Opportunity...