The Code of Standards states that Civil Servants should give their names to any member of the public with whom they are dealing, except where given a special exemption, for example, on security grounds and ensure that members of the public are dealt with in a respectful manner.
(https://www.sipo.ie/acts-and-codes/codes-of-conduct/civil-servants/Civil-Service-Code-of-Standards.pdf).
Special exemption groups are a matter for individual employers based on specific circumstances/requirements in their organisations.
Additionally, guidelines for staff members related to correspondence are contained in each individual employer’s Customer Charter. The Customer Charter initiative was launched in December 2002. A Customer Charter is a short statement describing the level of service a customer can expect from a Government Department or Office. Under the initiative, each Government Department and Office is required to produce a Customer Charter and to report on performance against the service standards it sets out -
https://www.gov.ie/en/policy-information/a2c52c-customer-charter-initiative-guidelines/.