Follow the below steps to create a formula field that will give you the 18 characters ID of the records.

• Go to Setup | Customize | object name | click Fields
  (For Custom objects: Setup | Create | Objects | Object Name)
• In the related list “Custom Fields & Relationships” click New.
• Click the Formula radio button.
• Click the Text radio button for “Formula Return Type”.
• 6. Input the following Formula into the Formula Editor:
  CASESAFEID(Id)
• Set Field Visibility, add/ remove from Page Layout(s).
• Click Save.

NOTE: When dealing with record types only custom record types have ids.