Business interest expense
(3) Business interest expense(i) In general. The term business interest expense means interest expense that is properly allocable to a non-excepted trade or business or that is floor plan financing interest expense. Business interest expense also includes disallowed business interest expense carryforwards (as defined in paragraph (b)(11) of this section). However, business interest expense does not include amounts of interest expense carried forward to the taxable year from a prior taxable year due to the application of section 465 or section 469, which apply after the application of section 163(j). For the treatment of investment interest, see section 163(d); and for the treatment of personal interest, see section 163(h).