Hello, @CallaJ.

Depending on the QuickBooks version you're using, let me guide you on how to create a second company file in QuickBooks Desktop Mac and Windows. 

QuickBooks Desktop for Mac

1. Open QuickBooks Mac.
2. From the No Company Open window, click the Get Started button.
3. In the Create New Company, enter information about your company:
   • Company Name
   • Legal Name
   • Address/Country
   • Company Start Date
   • Income Tax Form Used
   • Federal ID
4. Click the Next button.
5. Select the type of business that comes closest to describing your company.

You can follow the same set of steps when creating a new company file. Once completed,  QuickBooks creates all the accounts that have a checkmark. You can refer to this article for more detailed steps: QuickBooks Desktop for Mac 2020 User's Guide (Go to page 4).

On the other hand, here's how to create a second company file in QuickBooks Desktop for Windows:

1. Open QuickBooks.
2. Click the File menu.
3. Select New Company from the drop-down list. 
4. 
5. Choose Express Start. 
6. Enter the new company’s name, address and contact information in the appropriate fields. 
7. Click Create Company.

You can browse these articles for more insights about creating a new company file: Start a new company file.

Keep me posted if you have other questions about managing your multiple company files in QuickBooks.