I access 2 company accounts with one email. How do I keep them separate?

You are allowed to purchase more than one QBO account with the same email address. Did you encounter any issue?

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It's good to see you here in the Community, @nancydjo. I can walk you through how to access two companies in one email within QuickBooks Online.

When you log into your QuickBooks, you can transfer one account to the master administrator. 

Here's how:

1. Click the Gear icon.
2. Select Manage Users.
3. Click the drop-down arrow in the Action column and choose Make master admin.
4. Select Make master admin on the pop-up that appears.
5. An invitation email will then be sent to the user to accept the role. 

For more details on the basics of transferring this process, I recommend reading the following article: How to Transfer The Role of Master Administrator.

Alternatively, I added this articles that will guide you more about managing your email and companies in QuickBooks:

Reset or change your login information for QuickBooks Online.
Sign in to multiple QuickBooks Online companies with one user ID in QuickBooks Online.

I'm happy we could make this right for you. Have a fantastic day.