Terms conveyed by means of policy in electronic business have become a common way to express permissions and limitations in online transactions. Doctrine and standards have contributed to determining policy frameworks and making them mandatory in certain areas such as electronic signatures. A typical example of limitations conveyed through policy in electronic signatures includes certificate policies that Certification Authorities (CAs) typically make available to subscribers and relying parties. Trade partners might also use policies to convey limitations to the way electronic signatures are accepted within specific business frameworks. Examples of transaction constraints might include limitations in roles undertaken to carry out an action in a given context, which can be introduced by means of attribute certificates. Relying parties might also use signature policies to denote the conditions for the validation and verification of electronic signatures they accept. Furthermore, signature policies might contain additional transaction-specific limitations in validating an electronic signature addressed to end users. Large-scale transactions that involve the processing of electronic signatures in a mass scale within diverse applications rely on policies to convey signature-related information and limitations in a transaction. As legally binding statements, policies are used to convey trust in electronic business. Extending further the use of policy in transaction environments can enhance security, legal safety, and transparency in a transaction. Additional improvements are required, however, in order to render applicable terms that are conveyed through policy and enforce them unambiguously in a transaction. The remainder of this article discusses common concepts of policies and certain applications thereof.