Some transactions, such as opening your first bank account in Turkey, require a tax number. Having and providing a tax number doesn't necessarily mean that you will owe taxes in Turkey. But having one is essential for getting certain things done, such as opening a bank account to deposit money, to prove you can support yourself financially, when you apply for a residence permit.
To get your tax number, go to any local vergi odası, or tax office. Tell them that you want a vergi numarası, or tax number. Give the clerk your passport. They will enter your information into a database, then give you your tax number. This usually takes around ten or fifteen minutes.
If you later become a legal resident of Turkey, you will be issued a kimlik numarası, or identity number, which will be printed on your ikamet tezkeresi, or ID card. Your identity number will then serve as both your identity number and your tax number.
If you are applying for a residence permit, there may be circumstances where you need an actual yabancı kimlik numarası (YKN, translated "foreigner identification number). If you don't yet have your residence permit, you can get a YKN by going to the Directorate General of Migration Management (DGMM) office responsible for your area and applying for one. This number will later be printed on your residence permit card.
If You Lose Your Tax Number
If you've lost your tax number and need it, you can look it up online here:
Here's a translation of what you will need to enter into the query form:
Soyad: Last name.
Ad: First name.
Baba Adı: Father's name.
Doğum Yeri: Select "Yurtdışı," at the bottom of the select menu, which means "outside of the country" if you were born outside of Turkey.
Doğum Yılı: Birth year.
Turkey Money and Banking Forum: If you have questions, please ask them in this forum.