Subject: INV5006687.pdf

This week I received an email with the subject "INV5006687.pdf." It came from someone I do not know at a company whose name I didn’t recognize, and it included an attachment. It stood out as junk, a message to delete. But as my right pinkie stretched to the Delete key, something told me to take a peek. I did.

To my surprise, INV5006687.pdf was not spam. The message had been sent by a company I know by another name. Attached was a PDF of an invoice for a classroom I had recently rented.

On business letters, it is acceptable to include a purchase order number or invoice number as a subject, introduced by the abbreviation Subj. or Re. But that doesn’t work in email–not with spam bouncing off the filters of companies everywhere. It definitely does not work when the reader doesn’t know the sender.

I would have recognized this subject immediately:

Invoice for Your Classroom Rental on November 28

Moral of the story: If you are sending an invoice by email, do not use the invoice number as a subject–not if you want payment. Only by pure luck will your reader hesitate before pressing Delete.



  1. Hi,

    One of the reasons for such kind of subject is windows. Typically, a company shall store it’s documents with invoice number etc. Now, if the company needs to send the document to you, it just right clicks on the document and selects the option ‘send INV5006687.pdf as email’. I am assuming that the company is using Microsoft Windows and Microsoft Outlook features.

  2. Chakshu, thanks for pointing out what happened. I had forgotten about that feature. So to communicate clearly, the person sending the email needs to take the time to change the subject.

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