With QB desktop, I have THREE entities. I cannot get all these in QB Online because I just have ONE email address!!!

You can sign up 3 different QBO accounts with the same email address. Did you encounter any issue?

https:// quickbooks.grsm.io/US

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Hi there, @ranchdadmom-gmai.

Thanks for coming to the Community. Allow me to share some insights about having multiple companies.

In QuickBooks Online (QBO), you can have as many companies as you'd like under the same QBO account. However, each company requires an additional subscription. You may access them with the same sign-in info. This lets you quickly switch between companies, which helps you manage everything more efficiently. 

To add a new company:

1. Go to the QuickBooks pricing page and select the subscription you want.
2. You’ll see a page that asks you to create an Intuit account to buy QuickBooks. Scroll all the way to the bottom and look for the small text that says “Adding a company to an existing account.” Select Sign in next to this. 
   
3. If you're signed in to QuickBooks, you’ll be asked to confirm the account you want to sign in with. If the account displayed is the one you want to use for the new company file, select Continue.
4. When asked, enter the same ID and password you already use for QuickBooks.
5. Fill out all the information about your new company and you’re good to go.

Once done, you’ll be asked which company you want to transfer your file to when converting from QuickBooks Desktop (QBDT). 

Be sure to let me know how these steps turn out and if you have further concerns while working in QBO. I'm here to lend a helping hand. Have a good one!