A business letter is formal written communication between organizations, individuals, or external entities for specific professional purposes. It usually follows standardized formats and includes expected elements like formal salutations, signatures, contact information, and a body of text focusing on one specific business purpose. The four essential parts of a business letter are the heading, which lists basic details; the salutation, used to greet the reader; the body, where you make your case or ask your question; and the sign-off, which shows you're finished and gives the recipient clarity on next steps. To write a business letter, one should first identify their purpose, find a contact, follow a consistent format, write with intention, keep it short, and copy edit. Business letters can be customized using templates or by creating new ones, and automation tools like Zapier can help streamline the process.