A contract is a legal agreement involving parties, activities, clauses and payments. The activities are to be executed by the parties satisfying the clauses, in accordance with the associated terms of payment. An e-contract is a contract modeled, specified, executed, controlled and monitored by a software system. In this paper, we study payment issues in e-contracts. Payments are meant for, and so are closely related to, the execution of activities specified in the contract. We consider (i) the payment amount for the execution of an activity, (ii) the time of payment relative to the execution and (iii) tracking the payment against the execution of the activity. For the first two, we use an execution model that enables representing a variety of states encountered in the generally complex executions of the activities in a contract. For tracking, we use a multi-level composition model for the activities. Our study brings out various issues that need to be addressed in designing a payment monitoring system.