There are two types of applications:

1) Application for allotment of TAN (Form 49 B)
In case you do not have a TAN, you can submit Form 49B which is the application form for issuance of TAN at the TIN Facilitation Centers established by NSDL or can apply online.

2) 'Request for New TAN Card or/and Changes or Correction in TAN data'
In case you want Change or Correction in data associated with your reformatted 10 digit TAN, you can use the "form for Change or Correction in TAN data" prescribed by ITD.

You can submit a duly filled-in application to any of the TIN-FCs managed by NSDL or can apply online.