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Level 1

QBCFMonitorService locks external USB drive

Windows 10 QB Desktop Premier 2020 user.


I have an external USB drive, mapped to a drive letter.  Not used for anything QuickBooks.  Now that I run QB Desktop (since recently) I can no longer eject this USB drive, probably any time after reboot once I have run QB.  I get Windows error "a program is using this device, go close it".


I used Task Manager and Event Viewer to discover that it is the QB Windows service "QBCFMonitorService" which is holding this drive open.  I killed the process and, lo and behold, I can now eject the drive.  This is very irritating!


Please remember, I have exited QB Desktop, and neither QB data nor executable resides on this drive.


1. Does anyone know what I can do to prevent this locking/holding open of whatever on an unrelated drive?


2. I have done a good Google and there is no information about *precisely* what "QBCFMonitorService" actually does/is for.  I am looking for more detail then the service description of "Quickbooks Company File Monitoring Service"!


QuickBooks Team

QBCFMonitorService locks external USB drive

Welcome to the Community, @jonbrave.


Let me share with you some insights about using an external USB drive in QuickBooks Desktop.


This problem occurs when your data is currently stored on a removable drive or online. I'd recommend moving your company files to your local hard drive before opening QuickBooks to avoid the same issue.


These are important best practices:


  • Practice storing QuickBooks files, including your company file, on your server computer’s hard drive. It is convenient to use online file hosting services like Dropbox, Google Drive, and, but they can cause issues.
  • Never store files on removable or external drives. External hard drives, USB flash drives, and Network Attached Storage [NAS] devices aren’t designed to run QuickBooks or multi-user networks.
  • Don’t encrypt your QuickBooks files or the hard drive storing them. This can block your multi-user network connection.


I'd also recommend checking on how to fix QuickBooks Desktop install errors.


Get back to me if you have any additional questions about using an external USB drive. I'm just a post away.

Level 1

QBCFMonitorService locks external USB drive

Thank you for replying.


However this is a stock answer which does not apply to my situation, as I described in my post.


I have made clear that the removal USB drive has nothing to do with Quickbooks.  It's just a drive used for other purposes.  It has no data or executables or configuration files related to my use of QB Desktop.


That is the point of the question.  Why is QBCFMonitorService choosing to keep something open on that drive, and can I stop it doing so?


QBCFMonitorService locks external USB drive

Thanks for getting back here, @jonbrave.


Let's take a few troubleshooting steps to help you eject your external USB drive seamlessly so you can get back to working order.


To isolate the issue, you can create a Windows firewall exception for QBCFMonitorService.exe. This will help ensure processes for multi-users won't intervene with other computer tasks. Here's how:


  1. Click the Windows Start menu.
  2. Type "Windows Firewall" into the search and open Windows Firewall.
  3. Click Advanced Settings.
  4. Right-click Inbound Rules (later on, you'll create Outbound Rules). Then, choose New Rule.
  5. Click Program and then Next.
  6. Select This Program Path and then Browse.
  7. Find and select one of the executable files on the chart above. Then click Next.
  8. Select Allow the Connection and then Next.
  9. If prompted, make sure all profiles are marked. Select Next.
  10. Create a rule. Give it a name like "QBFirewallException(name.exe)." or QBFirewallExceptionQBCFMonitorService.exe.


For more info about the process, please head to the Create Windows firewall exceptions for QuickBooks programs section of this article: Set up firewall and security settings for QuickBooks Desktop.


If you're using an antivirus program, I recommend reaching out to their support team for guidance on how to create exceptions. 


Also, to further help you do any of your QuickBooks tasks, you can always reach out to our Technical support team. 


Feel free to post a comment below, if you have additional concerns about QBCFMonitorService locking your external USB drive. I'll be always around to lend you a hand. Have a good one.

Level 1

QBCFMonitorService locks external USB drive

Thank you for replying.


However this too, like the previous suggestion, seems to be a stock answer which does not apply to my situation, as I described in my post.


No, setting firewall exceptions for QBCFMonitorService.exe does not alter the situation.  Nor can I see why it would, or how it could have anything to do with the problem.


No, there are no other users of the QB, nor any network involved.  I am the only user.  I don't see any relevance for firewall or network.


As I have said each time, I simply have a completely unrelated USB external drive in the PC.  There is nothing QB on that drive.  I don't even have to have run QB since reboot.  Yet QBCFMonitorService.exe still "locks" it.  So that on trying to eject it I get Windows error


Problem Ejecting USB Mass Storage Device
This device is currently in use. Close any programs or windows that might be using the device and then try again.


I have to kill the running QBCFMonitorService.exe process, then I can eject the drive.  I don't want to have to do that all the time.


Please, no stock answers, someone needs to read what I say and explain what & why QBCFMonitorService.exe is doing on an unrelated T: drive which just happens to be plugged into the machine, and what I can do to prevent it so that I can eject the drive when I want to?

QuickBooks Team

QBCFMonitorService locks external USB drive

I understand this wasn't an easy process for you, @jonbrave.


Thank you for checking out my colleagues' responses to your posts.


Since you're still experiencing the same issue, I suggest reaching out to our Customer support. This way, they can further investigate why the QBCFMonitorService is locking the external USB drive. They'll also share some fixes to resolve it.


Here's how you can contact support:

  1. Visit our webpage: QuickBooks Desktop Support.
  2. Click on Contact Us.
  3. Select QuickBooks Desktop.
  4. Select your concern from the What can we help you with? section.
  5. Choose how to connect with QuickBooks experts: Call Us or Message Us.

I'm also adding this handy article that you can access to reach support: Get help from QuickBooks Desktop support.


You can always reply to this thread if you have further concerns with your QuickBooks Desktop. Have a good one!

Level 1

QBCFMonitorService locks external USB drive

Ok, thank you, I'll do that tomorrow!

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