TAN or Tax Deduction and Collection Account Number is a 10 digit alpha numeric number required to be obtained by all persons who are responsible for deducting or collecting tax. It is compulsory to quote TAN in TDS/TCS return (including any e-TDS/TCS return), any TDS/TCS payment challan and TDS/TCS certificates.
and you can apply same from depicted link: An application for allotment of TAN is to be filed in Form 49B and submitted at any of the TIN Facilitation Centres meant for receipt of e-TDS returns. Addresses of the TIN FC are available at www.incometaxindia.gov.in or http://tin.nsdl.com.