Can I use two companies with the same email and password

It's nice to see you here in the Community, @susanpigney1955. 

Yes, you can use the same login credentials for your two companies. This way, you'll have the option to easily go between each companies accounts by clicking on the gear icon in the top right of QuickBooks Online by selecting the switch company option. 

If you haven't set up the second company, you can perform the steps below: 

1. Go to https://quickbooks.intuit.com/uk/pricing/. 
2. Choose the best plan for your business. 
3. Click Buy Now & Save. 
4. Click Create a new account. 
5. Enter the same email address, first and last name, phone number, and password. 
6. This step is the most important. Where it says Already have an account ? sign in. Sign in using your existing sign in details for the QuickBooks account you already have. It will then set up the new company with the same log in and you can then use the switch company option mentioned above.

I'm including these tutorial videos to help you get started using the program. You can also browse these helpful articles to assist you with all your product-related questions. 

This will get you back on track, @susanpigney1955. 

If you need anything else, please let me know. I'll be around to help.