COB meaning: close of business

What close of business means

COB is short for close of business, meaning the end of the working day, especially on a financial market. “By COB” asks for something before the office shuts today. “As at COB 30 June” in a report means the numbers were taken when the market closed that day, and anything that moved afterwards waits for tomorrow’s report.

The phrase turns up in purchase orders, tender deadlines and press notices, the formal places where an exact hour would serve better and somebody picked three letters instead.

It’s the formal end of the deadline shorthand in the jargon dictionary. The oldest example in one open dictionary is a 1997 membership directory, with COB written beside three separate deadlines. Who wrote it first is unknown.

Which hour COB lands on

COB names the closing, and closing times vary. A trading desk closes when the market does. An office that opens at 8 may treat 4:30 as close of business, and a support team on shifts may never close at all. The sender’s office decides, in the sender’s time zone.

So the three letters can mean very different afternoons. A request from Sydney marked COB lands in London before most people there have had breakfast.

COB, EOD and close of play

EOD is the same deadline tied to the day instead of the office, and most people swap the two freely. EOW stretches it to the last working day of the week. British and Australian offices add close of play, from cricket, or end of play. 10.6% of Australian office workers say they use one of those two.

Corn, swans and bread rolls

Lower case, cob is an old word with several unrelated jobs. It’s the core of an ear of corn, a strong horse with short legs, a small round loaf in Britain and a male swan. His partner is called a pen. Corn on the cob is why a search for the word serves recipes beside deadlines.

The word goes back to late Middle English, between 1375 and 1425. In a British office, a cob by COB is lunch with a deadline.

COB on an org chart and a circuit board

As an abbreviation, COB works in other places too. In a company it can mean chairman of the board. Electronics has it as chip on board, an LED module or chip bonded straight onto a circuit board. The US military uses it for a contingency operating base. Insurers use it for coordination of benefits.

The COB that arrives at breakfast

“You’ll have it by COB” is a promise with a soft edge. The work sometimes lands at 11:40 pm with a note saying it’s still technically today. Other times it lands at 8:50 am, sent as first thing, as if the night didn’t count.

Neither breaks the promise on paper, which is why a COB deadline from someone else needs an hour beside it. A 5 pm countdown helps you meet one. It doesn’t help when their close is 6.

Asking for COB with an hour in it

“COB Thursday, which for us is 4 pm Eastern” costs seven extra words and saves a Friday morning argument. It also gives the other person a fair way to say no in time. If 4 pm can’t happen, you hear about it at noon instead of the next morning.

When the deadline belongs to a system, say so. A payment run, a print slot or a courier pickup closes on the minute, whatever the office calls close of business.

When COB is also home time

Close of business is a deadline for the work and, on paper, the end of your day. The office that wants the report by COB can look surprised when you leave at COB. Somebody asks “leaving already” at 5:01. The full answer is yes, delivered while walking.

Leaving before the close takes an excuse, and the excuses to leave work early cover those afternoons. Walking out at the close takes none, because the office named the hour itself. On flex time, the close is the one you picked.

The Friday COB

A request for COB Friday, sent at 3:55 that afternoon, asks for your weekend with a business abbreviation on it. The sender logs off at 4 and reads your reply on Monday. If the work could wait until Monday, say so before you start it. A countdown to Friday at least tells you how much weekend is left to protect.

A COB request by email

Subject: Supplier invoices for September

Hi Tom, please approve the three supplier invoices by COB 4 pm, before the payment run Thursday. Accounts closes the payment run at 4:30, and anything approved after that waits until October.