It's a pleasure to have you in the Community today, @info1849. I've got your back, and I'll share some details about adding a new company to an existing QuickBooks Online (QBO) account.
Here in QBO, you'll need to sign-up for a new QuickBooks Online account to create another company. Also, please be aware that each company file has its own paid subscription, but you can access them with the same sign-in information. With this, you can switch between companies smoothly and manage everything more effectively.
See this article for more information: Create or add another company file to QuickBooks Online.
In addition, I've got you this article to help you manage payments in QBO: Record invoice payments in QuickBooks Online.
You can also check this page to learn more about how to track money moving in and out of your business and bank account: Track your cash flow in QuickBooks Online.
@info1849, our door is open 24/7 in case you have any additional QuickBooks-related concerns. You can also get back to me anytime if you need help performing specific tasks in QuickBooks. I'll be more than happy to help you out again. Take care, and have a nice day!