Once you start work, you will have to register for a tax number (Vergi Numerası). This is the rough equivalent of a social security number in other countries. To register, head to your local Finance Department (Maliye).
In most cases, the Maliye office will be located in the town or city hall. Bring photocopies of your passport, residence permit, and work permit to the Accounts Department (Defterdarlik). Once you find the Accounts Department, locate the Tax Department (Vergi Dairesi) and finally the Civil Test Service (Sivil Yoklama Servisi). Be patient during the trip – the labyrinth-like Finance Department is an appropriate representation of the Turkish social insurance bureaucracy.
Civil Test Service clerks will ask you for a dilekçe (petition). These “petitions“ are brief notes (written in Turkish) that politely request government employees to assist you. Though this is a required document, officials might complete one for you if your Turkish is not very good or you strike them as particularly confused. To be safe, however, prepare one in advance.
To complete your application, sign your dilekçe and get it signed by the Tax Manager´s Assistant (Vergi Müdür Yardımcısı).
You will then be issued a business card-size paper with your new tax number.