Cash flow management concerns the financial control and planning of a
firm's net cash inflows and outflows. In this paper, we develop a netw
ork model to represent cash flow problems that involve a decrease in m
arginal costs (or an increase in marginal revenues) as the volume of c
ash increases. This type of problem, referred to as quantity-based dis
counting, is converted to a minimum concave cost network flow model. B
y making this conversion, we are able to solve efficiently the quantit
y-based discounting problem using established algorithms. A short-term
money market investment problem is used to illustrate the mathematica
l models developed in this paper.