The Tax Identification Number (TIN) is a personal number used for tax purposes in your tax country (i.e. the country in which you report your taxes).
The term used for TIN varies from one country to another, for example: Identification Number, National Insurance Number, Social Security Number, etc. Accordingly, you will be asked to supply your TIN information.
Why do we ask for your TIN?
The Common Reporting Standard (CRS), developed in response to the G20 request and approved by the OECD Council on 15 July 2014, calls on jurisdictions to obtain information from their financial institutions and automatically exchange that information with other jurisdictions on an annual basis.