What do we have to do if we have been allotted a duplicate TAN by oversight?

In case duplicate TAN has been allotted, an application should be made for cancellation of the TAN which has not been used. Application for cancellation of TAN is to be made in the "Form for Changes or Correction in TAN" which can be downloaded from the website of NSDL NSDL website or obtained from any other source. The application is also available at TIN Facilitation Centres.