As of 16 April 2020, taxpayers of the Digital Services Tax (DST) can register, file their tax returns and make payments on the Turkish Revenue Administration’s website. The website is accessible via the following link: https://digitalservice.gib.gov.tr.
Source: KPMG
Source EY
Note: On the same website there is a link to the part where foreign business have to register for charging Turkish VAT on electronically supplied services.