ITR will not be taken up for processing u/s 143(1) of the Income Tax Act, until the PAN is linked to Aadhaar. Those who are required to link and have not done, complete the same by 31-08-2017.
Procedure to Link Aadhaar :
https://incometaxindiaefiling.gov.in/eFiling/Portal/StaticPDF/Procedure_to_Link_Aadhaar.pdf