COB Meaning — And How to Use It for Clear Communication

COB - Close of Business. Computer keyboard on the office table.

In business correspondence, it is normal to see a variety of acronyms used in place of common business terms — for instance, COB meaning. Over time, these acronyms become commonplace and easy to understand. However, when you first encounter a business acronym in an email, you might have questions about the specific meaning of the term.

One common acronym used in business emails is COB. In this article, we’ll not only define COB meaning but also how you can use it, best practices for using COB in an email, and tips for employers as they implement acronyms into daily correspondences with employees. Let’s get started.

What Is the Meaning of COB?

COB stands for “close of business.” This acronym is often used in emails to indicate either a deadline or to let the recipient know when to expect a report or response. However, when you are working with clients or employees across different time zones, what constitutes “close of business”?

In the U.S., close of business usually refers to 5 p.m. Eastern Standard Time, regardless of where you are located. This helps ensure that teams across time zones are on the same page.

Why is Eastern Standard Time used to indicate close of business rather than Pacific, Mountain, or Central Time? Professionally, most companies have adhered to this practice due to the closing of the stock market, which takes place at 5 p.m. in the Eastern Standard Time zone.

Examples of COB Meaning in Email

To help showcase the COB meaning in email, check out the following examples of how you can use this acronym to indicate a timeline:

Example 1:

Dear Mr. Sancko,

We look forward to adding your marketing data to our upcoming report to the leadership team. Please send over your department’s marketing data by COB (5 p.m. EST) on Friday, September 2, to ensure inclusion in our report.

If you have any further questions, please let me know.


Janice Langley

Example 2:

Hi Sarah,

I’m looking forward to including your slides in our marketing presentation to the digital transformation team. I am touching base to remind you to please have your final presentation slides emailed to me by COB on Monday, September 5, 2022.

If you have any further questions, please don’t hesitate to reach out.


Bernard Kringle

Example 3:

Hi Janet,

Thank you for completing the first step in applying for our marketing manager position. Please make sure that you have completed your application by COB (5 p.m. EST) on Friday, September 23, 2022, to be considered for this role.

If you have any further questions, please don’t hesitate to reach out.


Mary Rain


Another common acronym used in business correspondence that is used to indicate a timeline is EOD. EOD stands for “end of day” and carries a similar meaning to COB. However, the difference between COB and EOD is that EOD typically refers to the sender’s time zone. For example, if a manager writes to their employee and they both work in the U.S. in Central Standard Time, they might use EOD to indicate that a task should be completed by 5 p.m. Central Standard Time.

Common uses for EOD include the following:

  • All time card submissions are due by EOD.
  • Please make revisions to this document by EOD.
  • To be considered for this role, please submit your application by EOD.
  • To be included in our presentation, we request all slides to be sent over by EOD.

When using COB versus EOD, it is best to use COB to discuss deadlines with organizations or employees spanning time zones. EOD is better for communicating with team members who you know reside in the same time zone as you. For example, if you are messaging a colleague through an employee chat and you both work in the same office, you might request information for a project by EOD. However, if you were asking for the same information from an external source and you are uncertain of the time zone where they operate, it is safer to use COB.

Tips for Using COB in Business Correspondence

While COB can be a handy acronym for indicating a deadline or timeline for a project’s completion, it is important to use the abbreviation carefully. While you might understand COB meaning, that does not mean that everyone you correspond with does. For that reason, be sure to employ these tips when using COB in an email or letter:

  • Make sure to clarify: Along with the abbreviation COB, be sure to also include a timestamp and date. For example, rather than asking for a document to be submitted by COB, you should ask for a document to be submitted by COB (5 p.m. EST) on the Date, Month, and Year. This will help ensure that there is no miscommunication about a deadline.
  • Don’t repeat your ending: The acronym COB stands for close of business. As such, it is incorrect to type out COB business. In this case, the repeat of business is redundant.
  • Help new employees: When you work in a professional business setting for a number of years, it can be easy to grow accustomed to using acronyms. However, as new employees are hired, particularly those with little professional experience, these acronyms can be confusing. Make sure to help new employees learn important business acronyms. You can even outline acronyms your organization commonly uses in onboarding documents or employee resource guides. This will help prevent confusion and ensure that all employees are on the same page when communicating.
  • Don’t include the weekends: When referring to COB or EOD, avoid using these to indicate a deadline over the weekend. Traditionally, business days are only considered to be Monday through Friday. In some rare cases, you might indicate a weekend deadline due to a specialized project or when working with business associates that have weekend hours.

When writing business correspondence, clear communication is key. If you plan to use acronyms, such as COB or EOD, always pair these business terms with a concise explanation of deadline expectations.