1. A method for reconciling transactions, the method comprising: obtaining, by a transaction processing computing device and through a computer network, at least one transaction from each of at least two systems; applying, by the transaction processing computing device, at least one rule of a set of configurable matching rules, the at least one rule identified based on a comparison of the at least one transaction from each of at least two systems to the set of configurable matching rules; determining, by the transaction processing computing device, a value of a user defined function based on an application of the user defined function to a first result from application of a first function to the at least one transaction from one of the at least two systems that matches the at least one transaction from the other one of the at least two systems based on the applying and a second result from application of a second function to the at least one transaction from the other one of the at least two systems that matches the at least one transaction from the one of the at least two systems based on the applying, wherein the value of the user defined function is one of a null value and a residual value; applying, by the transaction processing computing device, configurable criteria data to the value of the user defined function, creating a residual transaction in one of the systems, and recalculating another value of the user defined function, when the value of the user defined function is determined to be the residual value; and reconciling, by the transaction processing computing device, the transactions, when the value of the user defined function is determined to be the null value.