.The portion of interest charged on a lending transaction between a flow-through entity (S corporation or partnership) and its partners or shareholders which represents a payment a person makes to himself or herself. Stated differently, it is the amount the lender/borrower reports as interest income/expense which is equal to the lender's/borrower's distributive share of the flow through entity's interest deduction. The interest payments received are generally treated as portfolio income..Small Business Taxes & Management 2.