According to sources, the I-T department has analysed data and found huge mismatch in the information provided by certain brokers to the stock exchanges.

"We have analysed the data. We found that in the short-term of three months during January-March 2009, more than five lakh transactions (where mismatches were found) in futures and options segment were of the order of Rs 25,000 crore," an official with Finance Ministry told PTI.

The bourses, which include National Stock Exchange and Bombay Stock Exchange, have to submit monthly statement to the Director General of Income Tax (Intelligence) within 15 days from the last day of each month.

The official further said the Income Tax intelligence department would keep close eye on these transactions so that any possible fraudulent practices can be avoided.

The stock exchanges should also look that the transactions in respect of cash and derivatives segment once registered in the system are modified only in cases of genuine error and maintain data regarding all transactions.

"The stock exchanges shall ensure that transactions in respect of cash and derivative market once registered in the system are not erased," the official added.

The details furnished by the bourses should include the transaction ID, broker name, name of the client, total value of transactions, scrip name, quantity, rate, PAN card of clients, among others.

In January this year, market regulator Sebi had warned brokers that any change in trade details of clients after execution would attract monetary penalty if the reason is not genuine.

The decision was taken to check any possible fraudulent activities by changing client details in the name of error and wrong data entry.

It had further said that stock exchanges can permit modifications to client code post trade execution only in case of genuine error or wrong data entry made by trading members.