We understand how important it is to stop accounts from being merged to ensure the accuracy of your accounting, @IT-User . However, please know that in QuickBooks Online (QBO), merging accounts or customers is a manual process.

QBO will prompt you with the option to merge if there is an existing account or customer with a similar name, as the system relies on names as the basis for identification. It cannot be undone once merging is complete.

To resolve merged accounts with identical names, you can create new accounts or customers with unique identifiers, such as Sample Customer 1, Sample Customer 2, and Sample Customer 3. This prevents future merging and ensures easier identification for linking transactions.

Here's how:

1. Go to My apps, then select Customer Hub.
2. Click on Customers, then select New Customer.
   
   
3. Enter the name with the identifier and complete other details.
4. Once done, click Save.
   

If the merged accounts contain transactions, locate and edit those transactions to link them to the newly created customers or accounts. This will help maintain accurate accounting records.

You can also use the Audit log to check if someone merges those accounts or customers. You can filter it by the date you noticed them being merged.

If you find that no one has merged the accounts, you can contact our Live Support team. They have the tools to securely review your account and determine why the accounts have been merged. They can also advise you on the next steps to resolve this issue.

Please feel free to revisit this thread if you need further assistance.