It's not mandatory to link your bank account with Aadhar card. The truth is that there has been no notification from RBI to mandatorily link a bank account with the Aadhaar number. By collecting Aadhaar details from their customers banks are trying to pre-empt the possibility of it becoming compulsory in future. Another reason why banks are ensuring of Aadhaar into a customer's account is to promote digital transactions by promoting Aadhaar enabled transactions without the use of debit and credit card. Currently, linking of Aadhaar with your bank account is to facilitate receipt of direct benefit transfer from the government.
Aadhar is used to establish a person's identity on the basis of demographic and biometric information. Aadhaar is a 12 digit number code, issued by the Unique Identification Authority of India. In addition according to the RBI's guidelines banks have to accept one of the six official documents for opening of an account including PAN card and Aadhaar. There is no requirement for an individual to produce both the documents for opening of a bank account.However, Linking of PAN with Aadhaar, will eventually end up linking your bank accounts with Aadhaar number. This is because bank accounts of the person would already have PAN. Once Aadhaar is linked with PAN, it will certainly lead to automatic link with the bank accounts as well.
Hence, the interconnection of PAN card, Aadhaar and bank accounts, implies that the government will be able to keep a track of your financial transactions. According to a recent notification by Income Tax Department, if you do not link your PAN card with the Aadhaar card within the stipulated time, it may lead to invalidation of your PAN card. If that happens, you will not be able to file your return this year as quoting of both PAN and Aadhaar has been made mandatory. The deadline for which is June 30, 2020. Not only linking PAN with Aadhaar, you also need to link your bank accounts with PAN by June 30, 2020.