Different communication methods are often required for different situations. More formal communication, such as reports, specifications, invoices or service level agreements, might be required for external relevant interested parties. For internal communication, methods such as daily contact, regular department meetings, briefing sessions, email or an intranet may be used. More formal methods such as written reports or job specifications could also be required for internal communication, depending on the nature of the information and how critical the issues are that need to be communicated.