Personal communication details (mobile phone, telephone, e-mail and Skype) can only be viewed by people who have access to the personnel files (e.g. HR department staff). These fields are optional. It is advisable to enter a telephone number, however, so that employees can be contacted on their private phones in cases of emergency. A personal e-mail address is also useful if, for example, important information has to be sent by e-mail to a member of staff who is ill or documents (e.g. certificates) have to be sent by e-mail to a former employee.