Imagine that the IRS is auditing somebody's tax return. The auditor thinks something is wrong with the return. However, he/she is not sure and does not have any hard facts on what is wrong. The auditor wants to read all the person's brokerage statements. However, he does not want to go to court to get a warrant to read them. Does the auditor need a warrant? Could the auditor just call up the brokerage firms and ask for the statements? Also as I understand it, the 1099s that the broker firm sends to the IRS has less information on it then the 1099s they send to the clients. Could the IRS get the client's version of the form without a warrant?
It seems to me, that under the US constitution the IRS would need a warrant.
I am in the United States