What does COB stand for? COB stands for “close of business.” It means the end of the working day, which in most US offices is 5 p.m. in the sender’s local time zone. When someone asks for something “by COB,” they want it before the business day ends.
What does COB mean at work?
COB is one of the most common deadline terms in business email. It comes from banking and finance, where “close of business” marked the moment a bank stopped processing transactions for the day. Today it is used in every kind of office.
The tricky part is that COB is tied to a place, not a clock. A 5 p.m. COB in New York is 2 p.m. in Los Angeles. If your team works across time zones, “by COB” can mean very different things to different people.
Some industries have a different close of business. Banks may treat a cutoff such as 2 p.m. or 3 p.m. as the end of the processing day. Retailers and hospitals may not have a clear close at all. When the exact time matters, ask.
You may also see COB Friday (end of the workday Friday) or COB tomorrow. Some people use COP (close of play), which is more common in British English.
Examples of COB in emails and messages
Email: “Please send the signed contract by COB Thursday.”
Slack: “Can I get your numbers by COB? Finance needs them first thing tomorrow.”
Teams: “Heads-up, the portal closes at COB today (5 p.m. ET).”
Client email: “We’ll confirm the delivery date by close of business on Monday, Pacific time.”
Reply: “Will do. Just to confirm, is that 5 p.m. your time or mine?”
COB vs EOD vs EOW
| Term | Stands for | Usually means |
|---|---|---|
| COB | Close of business | When the business day ends, often 5 p.m. local time |
| EOD | End of day | By the end of today, which some people treat as before midnight |
| EOW | End of week | By the end of the last workday of the week, usually Friday |
| COP | Close of play | Same idea as COB, more common in the UK |
COB and EOD are often used interchangeably, but COB tends to mean office hours while EOD can stretch to the end of the evening. Read more about EOD and EOW.
How to use COB correctly
- Add the time zone. “COB ET” or “5 p.m. PT” removes the guesswork for remote teams.
- Add the day. “COB” alone usually means today. “COB Friday” is clearer for later deadlines.
- Use a time for critical deadlines. For legal, financial or client deadlines, write the exact time and date.
- Confirm if you’re the one receiving it. A quick “Is 5 p.m. ET okay?” prevents late surprises.
- Write it out for outsiders. “By the end of the business day” is clearer for clients who may not know the acronym.
Related terms
Browse more short forms in our Workplace Acronyms hub.
FAQ
What time is COB?
COB usually means 5 p.m. in the sender’s local time zone, the typical end of the US business day. Some industries, such as banking, use earlier cutoffs.
Is COB the same as EOD?
They are close and often used the same way. COB usually means the end of office hours, while EOD can mean any time before the end of the day.
Which time zone does COB use?
By default, COB refers to the sender’s time zone. On remote or international teams, always state the time zone to avoid confusion.
What does COB Friday mean?
COB Friday means by the end of the business day on Friday, usually 5 p.m. local time.
Is it professional to write COB?
Yes. COB is standard in business email. For clients unfamiliar with it or formal contracts, write out the date and time instead.
