One should not assume that everyone has a surname!In my line of work, I have many clients (and not necessarily persons from non-European cultures) who do not have one, for historical reasons, or because of the way their birth certificates were issued. It is in fact incorrect to assume the surname of your parent / family / clan etc. without legally changing it, because you would be using a false name.Here is what I usually do in these cases:If the application is for something other than a legal document (like tickets), I write u2018Unknownu2022 or N/A (if the field allows the u201c/u201d character). Then I tell my client to carry at least a photocopy of the document showing no surname, to confirm it at the entrance / when picking up the ticket etc. Sometimes, someone calls back to confirm the situation and you can scan the document,If the application is in writing, or for a legal document, I leave the field blank and inquire when depositing it, with the person in charge, what their policy is. Usually they take it like that, and report to their superior.All in all, itu2019s not an easy life without a surname. Therefore, my advice is to follow the local administrative name change procedure (which usually happens at the local court or town hall), or change your name through Deed Poll if available in your country (like the UK), by choosing a surname for yourself.One well known example of a person who had no surname, and went through the administrative procedure, because of the bafflement of international contacts, is Dr Abdullah Abdullah, the Prime Minister of Afghanistan. He simply doubled his given name.