Close of Business (COB)

A close of business (COB) is the end of the business day. It is used to indicate when something should be completed by the end of the business day. 

In US business communications, COB typically signifies 5:00 PM EST or the end of the working day in the sender’s time zone. EOD (End of Day) and COB are often used interchangeably, but EOD implies the end of the business day in the recipient’s time zone.

For example, the tour manager sends an email stating that payment for the tour package must be received by COB Friday to secure a spot. The client must complete their payment by the end of business hours in the tour agency’s time zone. 

While COB is a common abbreviation, it’s important to ensure clarity regarding the specific time and date if there’s any uncertainty about time zones.