Abstract: A rule-based payment system is described that divides a payment among multiple parties by invoking one or more deduction rules. The rule-based payment system typically operates as part of a software application that provides many functions relevant to a real estate or other commission-based practice. Rules can be added to the system at any time without modifying the software. Rules are scripts that the software application can invoke to carry out deductions specific to a particular environment. If the software application manufacturer wants to provide the software to multiple markets in many different environments, the software manufacturer can provide a different set of rules for each environment without modifying the software application itself. Thus, the rule-based payment system allows software to be shared among many markets while still having the flexibility of custom-built software.