Ensuring Sales: A Theory of Inter-firm Credit

We propose a simple theory to account for the prevalence of interfirm credit at an interest rate of zero. A downstream firm trades off inventory holding costs against lost sales. Lost final sales impose a negative externality on the upstream firm. The solution requires a subsidy limited by the value of inputs. Allowing the downstream firm to pay with a delay is precisely such a solution. A reverse externality accounts for the use of prepayment. We clarify how input prices vary with such policies, and when trade credit/prepayment is more efficient than pure input price adjustments. (JEL D21, D62, D92, G31, L25)