To protect sensitive data like a government-issued ID number, encrypting the field and carefully managing access permissions is crucial. Here's a step-by-step guide on implementing this security solution:

Create the Custom Field:

Navigate to Setup.

In the Object Manager, select the relevant object (e.g., Contact).

Click on Fields & Relationships.

Create a new Text field for the government-issued ID number.

Enable Classic Encryption for Custom Fields:

In Setup, search for 'Encryption Policy'.

Enable 'Encrypt Custom Fields'.

Select the custom field you created for the government-issued ID and mark it for encryption.

Set Permissions:

Navigate to Setup.

Go to Profiles or Permission Sets.

Ensure only the necessary profiles/permission sets have the 'View Encrypted Data' permission:

Click on the relevant Profile or Permission Set.

In System Permissions, enable 'View Encrypted Data'.

Assign this permission only to those users who need to interact with the government ID data.

Adjust Field-Level Security:

In the Object Manager, select the custom field for the government ID.

Click on 'Set Field-Level Security'.

Ensure the field is visible only to the necessary profiles.

Remove the field from page layouts for users who should not access it.

Test the Setup:

Log in as a user with access to the encrypted data to verify they can view and interact with the data.

Log in as a user without access to ensure they cannot see the encrypted field.

By following these steps, you ensure that the government-issued ID number is encrypted and only accessible to authorized personnel, thereby protecting sensitive client data effectively.

Salesforce Security Guide: Classic Encryption for Custom Fields

Salesforce Permission Sets: Managing Permissions