If you have created a duplicate company in the system and added deals to both the original and duplicate companies, you will need to follow these steps to merge all deals into one company.

1.  Pick one of the companies you want to keep.  Rename the duplicate company to be able to identify it.  For example, if you had "Company A", change one to "Company A DUPLICATE".

2. Manually, add/modify any information in the duplicate company to the original.  

3. Go to the duplicate company deals.  Example go to all deals for "Company A DUPLICATE" and change the company of the deal to the original "Company A".  Follow these instructions in order to change a deal's company: How to change a company's Deal? 

4. Delete the duplicate company.