The COB acronym most often means close of business, the point when the workday wraps up. When a coworker writes "Please send it by COB," they want it before the office closes, which in the US is usually taken to mean 5 p.m. in the sender's time zone.
In health insurance, COB means coordination of benefits, the rules for which plan pays first when a person has two. And on a lighting package it can mean chip on board, a type of LED. The rest of this page sorts out which is which.
Quick facts
Main meaning
Close of businessInsurance meaning
Coordination of benefitsLighting meaning
Chip on board (LED)Type
Initialism, said C O BUsed in
Work email, deadlines, insurance forms, product labelsSame as
EOD, end of day, in most officesRelated
What does COB stand for in business?
In offices, close of business marks the point when the workday ends and the company stops handling new work. The idea comes from banking and trading, where a day's transactions are counted up after a set closing time.
- C for close, the end point.
- O for of.
- B for business, meaning the working day.
Because offices keep different hours, COB is a little vague. Many people read it as 5 p.m. Some teams mean 6 p.m., and a bank's cutoff for same day processing may be earlier. If the exact time matters, say it: "by 4 p.m. Eastern" leaves no doubt.
How COB is used in work email
Email from a manager: "Can you send the updated budget by COB Thursday?" This means before the end of Thursday's workday, in the manager's time zone if you work in different places. Sending it Thursday night or Friday morning would miss the deadline.
A few habits keep COB deadlines clear:
- Add the day: "COB Friday," not just "COB."
- Add the time zone when the team is spread out.
- Do not stack two short forms when one will do. "COB today" is fine; "EOD COB" is not.
- Reply with a clear yes so the sender knows you saw the deadline.
Note that COB on a Friday usually does not mean the weekend. Work due "COB Friday" is due before people leave Friday.
COB abbreviation meaning in insurance
On an insurance form, coordination of benefits is the process plans use when you are covered by more than one, such as your own job plan and a spouse's plan. One plan is named primary and pays first. The other, secondary, may pick up some of what is left. The aim is that the two together do not pay more than the total bill.
You may get a "COB questionnaire" asking whether you have other coverage. Insurers may hold claims until it is returned, so answering it quickly can prevent delays.
The COB acronym in other fields
| Field | Stands for | Example |
|---|---|---|
| Office work | Close of business | "Report due COB Monday." |
| Health insurance | Coordination of benefits | "Please update your COB information." |
| Lighting | Chip on board | "COB LED strip, warm white." |
| Military and travel | Close of business, often with a time | "Submit forms NLT COB." |
In lighting, chip on board means many tiny LED chips are mounted close together on one base, which gives a smooth band of light instead of separate dots. Learn more about the light itself on the LED meaning page.
There is also the plain word cob, as in corn on the cob, a male swan or a sturdy horse. Those are words, not abbreviations, and are written in lowercase.
COB vs EOD and other deadline letters
- COB vs EOD: both point to the end of the workday, and most offices treat them the same. EOD can sometimes stretch to the end of the calendar day, so COB sounds firmer.
- COB vs COP: close of play is a similar phrase heard more in British offices.
- NLT: no later than, often written before COB in government and military notes.
- ETA: estimated time of arrival, used when someone asks when you will be done.
To see more workplace shorthand, visit business acronyms.
Questions people ask
What is the COB full form?
It most often stands for close of business, meaning the time an office shuts for the day. In insurance it means coordination of benefits, and on lights it can mean chip on board.
What time is COB?
There is no fixed rule, but in the US most people read it as 5 p.m. local time. If the time matters, ask or give an exact hour.
Is COB the same as EOD?
In most offices, yes. Both mean the end of the working day, though some people read EOD as later in the evening.
Is COB an acronym or an abbreviation?
Strictly speaking, people say it letter by letter, "see oh bee," so it is an initialism, a kind of abbreviation. Everyday speech calls it an acronym too.
What does COB mean in health insurance?
It means coordination of benefits. Plans use it to decide which one pays first when you have more than one.