The full form of COB is Close of Business

COB is an acronym for “close of business,” which is the end of the business day. Most companies base COB hours on traditional U.S. business closing hours of 5 p.m. Eastern Standard Time. Stock markets use COB when referring to the time financial markets close. 

Business communications regularly include acronyms to help the sender quickly type frequently used language. Employees and other business professionals frequently use the term close of business to communicate the end of a traditional work day. This article defines close of business and explains when and how to use it in professional communications. 

Differences between COB and EOD 

EOD means “end of day” and refers to the end of the business day in the sender’s time zone. For example, if a manager in Kansas emails a remote employee in Florida asking for a task due at EOD, the task would be due at the end of the day in their time zone, which would be 5 pm. Central Standard Time. While they’re both referring to the end of the business day, COB always means end of the business day in the Eastern Standard Time zone. 

Sometimes, you need to clarify a specific time with clients or employees if they’re unsure of the acronym or your time zone. Use COB for existing clients and employees you’ve already clarified the meaning of “COB” with. Use the acronym “COB” when: 

• Giving an employee a deadline 
• Requesting projects or actions from clients by the end of the business day in Eastern Standard Time.