I think I have the solution.  It has worked for me so far; I hope it works for everyone else. 

Let me just say that QBO has provided NO help with this GLITCH and they either don't know they have it or don't want to admit to ONE MORE problem with QBO.

The problem IS NOT in:

Your bank or bank connection

Your computer

Your browser

Your file

Your settings

The problem is a GLITCH with QBO "CATEGORIZED" transactions in your banking section and the duplication is triggered when you start the Matching or Adding process.

After cleaning my register FIVE TIMES, OVER 3500 transactions each time, I finally figured out what the problem/glitch in QBO is and why this is happening over and over.  NOW is up to QBO to fix it so one else must go through this problem again.

Disclaimer: I was able to piece this together because the 5th time I had to clean my bank register I decided to VOID the transactions instead of deleting them (I was seeing a pattern before but I had no way to confirm it because I was deleting transactions) and that allowed me to confirm that the SAME transactions kept duplicating over and over.

Solution:

1. Go to banking menu

2. Select your bank or account that continues to duplicate

3. Go to categorized transactions

4. Compared transactions in the categorized section to the transactions duplicated in your register

In the categorized section select all transactions that are duplicated (select the ones with the C not R, so you don't have to reconcile again).

5. Clickundo at top.  That will put all of those transactions into your For review section.Once you do this, refresh your browser and you should see all the duplicate transactions disappear from your register.

6. Then Click For review, select all the transactions that were undone and put back in here and click exclude to remove them.

I hope this helps everyone, Happy New Year all!

Brenda