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This guide is provided by Conductor, the service that powers the QuickBooks Desktop integration for many business tools, including the one that sent you here.
Most QuickBooks Desktop users work in a single company file, the local file that holds all of a company’s accounting data. If you work with multiple company files on the same Windows computer, you can still sync each file with your QuickBooks Desktop integration. The key is that every company file gets its own Web Connector connection and QuickBooks Desktop must stay open with no file loaded. This guide explains exactly how to set that up, why the “blank” QuickBooks window is required, and what performance trade-offs to expect.

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1. Create a Web Connector connection for each company file

You will run your integration’s usual QuickBooks Desktop setup flow once per file.
1

Open the first company file in QuickBooks Desktop

Start QuickBooks Desktop and open the company file you would like to connect first. Sign in as the Admin user.
2

Run the QuickBooks Desktop setup flow for your integration

Follow the on-screen steps exactly as you would for a single-file installation. When you finish, a new row appears inside the QuickBooks Web Connector that is linked to only this company file.
3

Close the first file, open the next company file, and repeat

Close the first file, open the next company file, and rerun the setup flow. Keep repeating until every company file on the machine has its own connection.
When you are done the Web Connector will look similar to the screenshot below, one connection per company file:
QuickBooks Web Connector with multiple connections

The Web Connector after creating multiple separate connections – one per company file.

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2. ❗ Keep QuickBooks running without any company file loaded

QuickBooks Desktop must stay open with no company file whenever your integration needs to sync data. This lets the Web Connector open the correct file on-demand, complete the request, and then close it again.

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How to return QuickBooks to the “No Company Open” screen

  1. Open QuickBooks Desktop.
  2. Go to the “File” menu.
  3. Select “Close Company”.
The QuickBooks Web Connector has certain limitations when working with multiple company files on a single computer:
  1. The Web Connector can only talk to one company file at a time.
  2. It only talks to the file that is currently open in QuickBooks Desktop.
  3. It will not force QuickBooks to switch files if another user already has a different file open.
However, if QuickBooks Desktop itself is open but no company file is loaded, the Web Connector is allowed to:
  1. Open the file that matches the incoming request.
  2. Process the queued operations.
  3. Close that file again, returning QuickBooks to the blank state.
That simple workflow makes it possible to serve multiple company files from one computer without disrupting anyone’s work.
QuickBooks Desktop without any company file loaded

QuickBooks Desktop showing the required "No Company Open" window.

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3. Sync one company file at a time

The Web Connector works on one company file at a time. For each sync it opens the company file, which takes 20 to 40 seconds, runs that file’s requests, waits 10 seconds for more requests for the same file, then closes the file. While it works on one file, requests for the other company files on this computer wait their turn, and the Web Connector does not check in for them. To keep requests from timing out while they wait, finish one company file’s API requests before you send API requests for the next. Requests for the same file that arrive within 10 seconds of the previous response reuse the open file; requests for other files sent at the same time have to wait and can time out. If requests for several company files overlap, these errors can appear even when everything is set up correctly:
  • “Your QuickBooks Desktop connection is not active” with a last active time of a minute or two ago: the Web Connector is busy with another company file. Wait for the other requests to finish, then try again.
  • “Request timed out … before it was sent to QuickBooks Desktop”: the request waited too long behind requests for other company files. Try again once the other requests finish.

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4. Best practices for a reliable multi-file setup

  • Use a dedicated Windows server: Most users managing multiple company files already have a Windows server in their office dedicated to managing their QuickBooks Desktop company files. Set up the Web Connector connections on this server and keep QuickBooks running there instead of on someone’s everyday workstation. That prevents a user from accidentally opening the wrong file and blocking syncs.
  • Launch QuickBooks Desktop after reboot and Windows sign-in. Add QuickBooks to the Windows user’s Startup programs, and ask your IT team to configure that Windows user to sign in automatically for unattended reboots. This ensures QuickBooks Desktop opens after the computer/server restarts, which eliminates the extra delay of QuickBooks Desktop having to launch every time you sync.

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5. Troubleshooting tips

  • If a sync fails because a different company file is open, someone opened a company file in QuickBooks Desktop on this computer. Go to “File” → “Close Company” to return QuickBooks to the “No Company Open” screen, then try again.
  • Make sure only one copy of QuickBooks Desktop is installed. Multiple versions can confuse the Web Connector. See our guide on ensuring only one version of QuickBooks Desktop is installed.
  • If an error says “Your QuickBooks Desktop connection is not active” and it was last active more than a few minutes ago, follow our guide to troubleshooting this error. If it was last active a minute or two ago, see “Sync one company file at a time” above.