(a) Mortgage interest of $600 or more Any person- (1) who is engaged in a trade or business, and (2) who, in the course of such trade or business, receives from any individual interest aggregating $600 or more for any calendar year on any mortgage, shall make the return described in subsection (b) with respect to each individual from whom such interest was received at such time as the Secretary may by regulations prescribe. (b) Form and manner of returns A return is described in this subsection if