COB

Close of Business

A business acronym used to specify a deadline or the end of a working day, typically referring to 5:00 PM in the local time zone of the business or recipient. It is most often used in internal communications, project management, legal documents, and vendor agreements to clarify when an action or deliverable is expected.

The term helps eliminate ambiguity in professional settings where time sensitivity matters. For example, a manager might say, Please submit the report by COB Friday, which implies the report is due by the end of the standard business day on Friday.

While COB is often understood to mean 5:00 PM local time, it’s essential to specify the time zone when working across regions or with remote teams (e.g., COB EST or COB Pacific Time) to avoid confusion. In global contexts, alternatives like EOD (End of Day) or using a specific timestamp (e.g., “by 17:00 UTC”) are often clearer.

Ultimately, while COB provides a useful shorthand in business, best practice is to clarify time zones or provide exact times when precision is required.