I have 3 small business can I put all onto one account

Let me provide some information on how you can handle multiple accounts in QuickBooks Online (QBO), essentialmugs40-.

We can have multiple companies under the same QBO account. Wherein, each company file has its own paid subscription, however, you access them with the same sign-in info. This lets you quickly switch between companies so you can manage everything more efficiently. If you have multiple companies under separate accounts in QuickBooks Online, here's how to move them all into one account. To learn more about this one, see the Create or add another company file to QuickBooks Online article. 

Just in case you'll need to delete the other company file and it is less than 60 days, just purge that company. Here's how: 

1. Go back to QBO and edit the URL in your browser's address bar. Delete everything after the last / and enter purgecompany. For example: https://...qbo.intuit.com/app/homepage, change to https://...qbo.intuit.com/app/purgecompany.
2. Type in Yes to confirm that you want to delete your company data.
3. Select Wipe data.

However, if the account is already 60 days old or beyond, I suggest canceling the duplicate subscription. With that, QBO will automatically delete the other company after 365 days. Please follow the steps to cancel your subscription:

1. Login to QBO and choose the duplicate account you wanted to cancel.
2. Go to the Gear icon ⚙ and then select Account and Settings.
3. Choose Billing and Subscription.
4. Under the QuickBooks section, click Cancel.
5. Follow the steps to cancel your account.

For the complete details on how to cancel your subscription, check out the Cancel your QuickBooks Online subscription or trial article. Feel free to visit our Account management page for more insights about managing your Intuit Account.

The Community always has your back, and I'm just a post away should you ever need anything. Just leave a comment below and I'll get back to you. Have a great day ahead. 

@essentialmugs40- 

One QBO account is for one company file. You can manage branches/divisions by utilizing the Class/Location feature available in QBO Plus. Otherwise you should open a new account.

https://quickbooks.grsm.io/UK

Another option, if you don't need to comply with MTD requirement, consider using a one time license of QB Desktop 2019 to manage multi company files.