QuickBooks is an innovative accounting software made by Intuit and used and by millions of small and mid-sized businesses around the world. It undoubtedly makes the task of managing a business incredibly simple. Though, like any other software in the world, QuickBooks too receives errors and glitches at times. According to the Intuit, QuickBooks Error code 6123, 0 “Connection to the QuickBooks company file has been lost” generally occurs in multi-user environments.

However, some messages can be fixed by simply following the instructions offered by the software, some may be intricate and unintelligible. There might be multiple reasons for this error to occur. When establishing or when the use of a QuickBooks company report over a network, you see one or more of the following errors:

The image as shown below is similar which appears on your desktop.

QuickBooks Error Message 6123-0

What Causes QuickBooks Error Code 6123, 0?

QuickBooks Error Code 6123, 0 is generally caused by one of following reason

  • The main computer has a corrupt network connection.
  • Firewall network is blocking a port needed to communicate with the server hosting the company file.
  • Damaged QBW files.
  • Corrupt QuickBooks data or program files.
  • Your system has multiple QuickBooks database services are running.
  • Same company file is open in a new version of QuickBooks.
  • You are restoring a backup from a flash drive or from a removable storage device.
  • Damaged Window user.

Steps to Fix QuickBooks Error Code 6123, 0

QuickBooks Error 6123, 0 is an intricate issue. However, you can use the following solutions to get rid of it.

Solution #1 – Use QuickBooks File Doctor tool

  • QuickBooks File Doctor is an excellent tool to fix some of the most common causes that trigger QuickBooks errors.
  • You can download this handy tool from here.
  • Once the QBFD tool is download. Then install it and run on your system.
  • It will display you the possible damages in data or company file that may be causing this error 6123.  
  • You will have two options to fix the damages shown in the result you received after running the tool:
    • You can restore the backup of company files.
    • If you are not able to open your company file, send your company file to QuickBooks data recovery Team.

Solution #2 – Install and run QuickBooks Connection Diagnostic Tool

  • On your host (main) computer, check my network connection. Install and run the QuickBooks Connection Diagnostic Tool.
  • Move to the next solution if the above mentioned solutions don’t work for you.

Solution #3 – Fix damaged Data files

If the Error Code 6123, 0 still exists after trying solution 1 and 2, follow the following steps to fix the network data file.

  • Press the “Windows key (Start button)” and click “Explore“.
  • Check your Company file and right click the file with “.ND” extension.
  • Rename it to “.ndold”

Important: If you still fail to fix the network data file QuickBooks Error 6123, 0, you will also not be able to switch to multi user mode.

To switch to multiple user mode you can do the following:

  • Go to “File” menu.
  • Then Select “Utilities”
  • Host multi-user access.
QuickBooks Error Code 6123
  •  Go to “File>Switch” to Multi-user mode
QuickBooks Multiuser Mode Error 6123

Important Note: In the unlikely event that the company file cannot be opened, the option to “Switch to multi-user mode” will not be available.  In that case, go to File>Utilities>Host multi-user access.


We hope that this article will assist you with everything you should know about QuickBooks Error Code 6123, 0. You can try the solutions mentioned on this page and fix the error if it pops up on your screen. If you still have any trouble, or you face any other QuickBooks related issue, you can contact our QuickBooks error support and our QuickBooks help & support Team will be glad to offer you quick and precise solutions.


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