Permanent Account Number (PAN) is a ten-digit alphanumeric identifier, issued by Income Tax Department. Each assessee (e.g. individual, firm, company etc.) is issued a unique PAN.
The IT Dept can get all the details of Bank Transactions where you have quoted your PAN number. PAN is necessary while opening an Account and the Transactions where higher amounts are involved will be noticed by IT Dept. The Income details and other information can be collected by the IT Dept with the help of PAN.