You can have two company files open in QuickBooks Accountant and Quickbooks Enterprise – this is a very useful feature.
Click on File on the menu bar.
From the File drop down menu – click on Open Second Company.
You will now see that the first file you opened will be labeled Primary File and the second file is labeled Secondary File.
There are some restrictions having two company files open.
You can review a list of restrictions at the QuickBooks support site: