If certain fields should not be edited after its creation, it is possible to make the fields read-only for all or specific users/user profiles. This quick guide will explain how to do this.
Please note that only System Administrators are able to make fields read-only. Also, depending on your setup, some fields or field definitions may differ.
Step 1: First, decide on which object the field you would like to make read-only, is available. Then go to Setup on the top right side of your screen
Step 2: You see a menu on the left hand side of your screen. Click on Create (which can be found under Build) and then click on Objects.
Step 3: Open the previously determined object, for this instance the object Step will be used as an example.
Step 4: Go to Custom Fields & Relationships and click on the name of the field you would like to make read-only
Step 5: On the top of the screen you will now see the button Set Field-Level Security. Click on this button
Step 6: In this screen you can tick off the boxes of the profiles you want the field to be read-only for. It is also possible to make the fields invisible for selected profiles. Click Save when you are done.
Step 7: This should make the field read-only for the selected profiles, unless they have Edit access through the permission set. You can check this by looking up a specific user by going to Setup - Administer - Manage Users - Users
Step 8: Scroll down to Permission Set Assignments, and open the available assignment, if applicable.
Step 9: Go to Object Settings and open the object the field you would like to make read-only, is related to. For example, if you would like to make the Rejection Date read-only, go to the object Steps
Step 10: Go to the header Field Permissions and scroll down to the field you would like to make read-only. If the checkbox in the left column is ticked, the user has read access. If the checkbox in the right column is also ticked, the user also has edit access. If both boxes are checked, you need to clone the Permission Set Assignment and uncheck the edit box in the cloned assignment, so that the before mentioned steps will have the desired outcome. How you can clone a Permission Set, will be explained in this article.