The gapping comma
The gapping comma is very simple. It is used to avoid repetition and to show that words have been left out.
For example:
The blue files contain invoices from 2012; the red files, from 2013.
The words that have been left out are “contain invoices”.
Another example:
The matrix is split into two parts: one encompassing the changes made to the draft by PP; the other, by TH.
The words that have been left out are “encompassing the changes made to the draft ”.
Now look at this example:
An appeal is examined within 21 days, and a complaint, within 60 days of the date they are filed.
Here the words that have been left out are “is examined within”.
I have used a gapping comma here, but it’s not really necessary, as you see below:
An appeal is examined within 21 days, and a complaint within 60 days of the date they are filed.
So you have a choice with gapping commas – don’t use one if the sentence makes sense without it, but put one in if you’re doubtful.
Common Mistakes in Business English 
You have yourself used two commas in a sentence which is reproduced below:
“I have used a gapping comma here, (comma) but it’s not really necessary, (comma) as you see below”
Do you think the use of second comma here is justified? I am looking forward to hearing from you.
Hi Pranjal, I take your point. The second comma is not strictly necessary. I do, however, often put a comma before “as” where the “as” introduces a longer part of the sentence. So I guess it’s a habit. Well done for noticing it!