The Visa End Date field will only be available if the eligibility to work type on the employee's profile has been selected as 'Passport and Visa number'.
To add the Visa End Date:
Search for the employee and go to their profile.
Click Person, then Profile.
Scroll down to Eligibility to work and click Edit.
Select the Nationality and then a type of identification that has been set up as Passport and Visa number.
Enter the date in the Visa End Date field.
Click Save.
Once this is done, you can also set up a visa end date notification based on the date in this field.