​ How does Income Tax Department ensure that PAN is quoted on transactions in which quoting of PAN is mandatory?

​It is statutory responsibility of a person receiving document relating to economic or financial transactions notified by the Central Board of Direct Taxes (CBDT) to ensure that PAN has been duly quoted in the documents in which quoting of PAN is mandatory. Thus, the receiver of these documents will ensure that PAN is quoted in the respective document. E.g. PAN is necessary to open a bank account and hence the Bank will ensure that the applicant has quoted his PAN at the time of applying for bank account.