I have a customer that has a problem with tasks in outlook that has been duplicated after a moving of data. The problem is that he original had over 2500 tasks, but he has now over 5000 tasks that he need to be removed. He is running outlook 2013 and exchange 2013.

Per your post, I am not clear what causes duplicate tasks showing in Outlook. Without tools, we may filter the task item and remove the duplicate ones manually. Please perform the steps in this article: http://www.howtogeek.com/howto/microsoft-office/prevent-outlook-with-gmail-imap-from-showing-duplicate-tasks-in-the-to-do-bar/

Of course,we may easy to delete these duplicate things by the other tool, like

http://download.cnet.com/Outlook-Duplicate-Remover/3000-20411_4-75218461.html

http://news.cnet.com/8301-13880_3-9956577-68.html

Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

They are free and easy to use.

Cheers,
Tony Chen
Forum Support
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It happend after a tech in our firm was to load some tasked that have been rescued from an crashed account. He did not check the box for not copy identical tasks during the process. 

The first link you sent was only for tasks that are in the to-do flagged elements. That is not the problem. 

The second link is only for outlook 2003 -2010 and not for 2013. I have tried them already.

There might be a lot of such remove duplicate add-ins or tools which supports for Windows 8 upon website. Most of them is free or Trial Version.

e.g.

http://www.office-addins.com/-outlook-addins/duplicates-remover-for-outlook.php

http://www.slipstick.com/addins/duplicates-addins/remove-duplicate-contacts-from-outlook/  "Tool" Section

Cheers,
Tony Chen
Forum Support
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Come back and mark the replies as answers if they help and unmark them if they provide no help.
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Hi,

Just checking in to see if the information was helpful. Please let us know if you would like further assistance.

Cheers,
Tony Chen
Forum Support
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Come back and mark the replies as answers if they help and unmark them if they provide no help.
If you have any feedback on our support, please contact tnmff@microsoft.com.

Hi,

I'm marking the reply as answer as there has been no update for a couple of days.
If you come back to find it doesn't work for you, please reply to us and unmark the answer.

Cheers,
Tony Chen
Forum Support
________________________________________
Come back and mark the replies as answers if they help and unmark them if they provide no help.
If you have any feedback on our support, please contact tnmff@microsoft.com.