On My Profile page in the personal details section an additional field is available which is used to capture the National ID. This field might not be visible if the feature is not activated in your company.

National ID can be setup to be different for different companies, for example in a company based in India it could be Passport Number and for a company based out of USA it could be Social Security Number. If can also be different for Local and Expats.

If an employee is transferred across companies which have different National ID then it will have to be added again after the inter company transfer is done.

This feature can be enabled by the Application Administrator from HRIS setup. Refer article - "National ID Setup" for more details.