Investment structure is the configuration of capital and instruments used to fund a selected business — the combination of debt, equity, and blended capital sources, their relative proportions, and their placement in the capital stack. Defining and drafting the investment structure requires an assessment of the investment's financial and impact effectiveness using a methodology such as the Impact Internal Rate of Return (Impact IRR). Selection factors include goals, risk tolerance, the type of impact investment (market-rate, below-market-rate, or blended), and the type of financial instrument (debt-based or equity-based).