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When Your COB Is My EOD

The other day in a business writing class, I read an abbreviation that perplexed me. Here is the sentence:

We need your contributions by the COB on December 14.

The writer, Linda, was asking for contributions for an adopt-a-family holiday program. Do you recognize COB? I strained my brain to think of what it might be, but I could not come up with anything.

graphic stating the importance of spelling out abbreviations

Linda was surprised by my ignorance. She thought everyone would recognize COB as “close of business,” as in the close of the business day. But I know the close of the business day as EOD, “end of day.”

Linda countered that everyone in her organization uses COB, so the employees, her readers, will have no difficulty understanding her message. Or will they? A coworker pointed out that COB has another meaning in their organization: California-Oregon border.

I wondered for a moment whether any employees might leave their contributions by the California-Oregon border. I have to admit that is extremely unlikely, but the potential for confusion still exists.

Linda agreed and simplified her sentence:

We need your contributions by noon on December 14.

That approach will work fine as long as her readers are in the same time zone.

Take a moment to check your writing for abbreviations and acronyms. Will your readers know that DC is the distribution center, or will they be thinking of the District of Columbia, discount code, or Divorce Court? Make it easy for them. Spell it out.


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By Lynn Gaertner-Johnston

Lynn Gaertner-Johnston has helped thousands of employees and managers improve their business writing skills and confidence through her company, Syntax Training. In her corporate training career of more than 20 years, she has worked with executives, engineers, scientists, sales staff, and many other professionals, helping them get their messages across with clarity and tact.

A gifted teacher, Lynn has led writing classes at more than 100 companies and organizations such as MasterCard, Microsoft, Boeing, Nintendo, REI, AARP, Ledcor, and Kaiser Permanente. Near her home in Seattle, Washington, she has taught managerial communications in the MBA programs of the University of Washington and UW Bothell. She has created a communications course, Business Writing That Builds Relationships, and provides the curriculum at no cost to college instructors.

A recognized expert in business writing etiquette, Lynn has been quoted in "The Wall Street Journal," "The Atlantic," "Vanity Fair," and other media.

Lynn sharpened her business writing skills at the University of Notre Dame, where she earned a master's degree in communication, and at Bradley University, with a bachelor's degree in English.

22 comments on “When Your COB Is My EOD”

  • I found your article because … wait for it … COB was in a communication from a colleague in our company and I had no idea what it represented. Interesting in your example, the two would mean the same, but EOD might also be midnight (time zone issues aside), and that the correction inserted an entirely different submission point (unless business closes at noon).

  • Typically, COB would be by 5pm and EOD before, well technically midnight, but basically to convey to the other person to expect the report/file/whatever the next morning. Both when used refer to the time zone in which the user of the abbreviation is (unless specified otherwise)

  • Hi Lynn,

    I found your article by searching “COB vs EOD” just before sending out an email. To confuse things even further, the person I’m writing previously used “EOB”. I certainly knew they meant “End of Business” but I wanted to stick with “COB” since I used it exclusively during 9 years in the USAF (where acronyms were a way of life!). Thanks for your article!

  • I found this while looking for a reason why anybody in their right mind would use EOB. COB is a more useful acronym because it can be pronounced like a word, Phonetically.
    IE:”I need your proposal by cob wednesday.”
    “I need your proposal by eeeahb?”
    If you are composing business correspondence, you should have the intellect to decipher COB from the context of the message. You already knew that eOB was end OF BUSINESS. What possibly could COB mean?! Oh my, I’m so frazzled. Get Real.

  • That’s funny! I have heard COB for years and years and only just encountered EOD for the first time this week. I just searched on these terms to confirm whether EOD meant the same as COB (actually, I was hoping it was midnight!)

  • I’ve always used and have experienced others using EOD…until today. Your article came up in my search as I racked my brain on what COB meant. Perhaps COB vs. EOD popularity is determined by region within the U.S.? I’m in the Southwestern part of the country.

  • Found this because was not sure what COB means =))

    EoD might be problematic as well – as in finance this means “Event of Default”.



  • This is a clear message:
    Please deliver the purchase offer by 17.00 Los Angeles time on Friday 12 November 2013.

    Unless it is an internal memo within the same company, this is an obscure message:
    PLS deliver your PO by COB 11/12

  • There you go. I was perfectly familiar with COB, but found your blog when I was wondering what my European colleagues meant by EOD.

    However, if I stay back to work on something, my ‘EOD’ is when I finish, or midnight, whichever comes first.

  • COB also can stand for “Continuity of Business” that ensures critical business functions continue to exist as normal, often used in business disaster recovery planning.

  • What is “TS” in relation to someone saying “by COB” then the respone was “why not by TS” – does anyone know? thanks – Jo

  • Hi, Jo. I am afraid I do not know. Why not ask the writer?

    Unfortunately, I have had to close comments on older posts because I am being killed by spam comments. They flood the site and my inbox. Sorry!


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