An abbreviation for indication of interest; a phase of the offering process during which the underwriter gathers information about the initial demand for the deal. In other words, indication of interest is a measure of investor demand for an initial public offering (IPO) whereby investors state how much securities they would like to purchase and the time the transaction would be completed.

The underwriter needs a reliable indication of interest when building the book prior to the offering. Indication of interest is one of many factors that the underwriter will consider to set the offering price for the IPO.