QuickBooks Error Code 12, 0 is a common error that occurs when you are trying to open or access a company file in QuickBooks. This error usually occurs due to the following reasons:

1. The company file is stored in a read-only network folder.
2. The file is being accessed by multiple users simultaneously.
3. The user does not have sufficient permissions to access the file.

Here are some steps you can take to resolve this error:

1. Open QuickBooks as an administrator: Right-click on the QuickBooks icon and select "Run as administrator". This will give QuickBooks full access to your system.

2. Check file permissions: Make sure that the user account you are using to access the company file has sufficient permissions to access it. To do this, right-click on the folder containing the company file and select "Properties". Go to the "Security" tab and check if the user has full control or at least read and write permissions.

3. Move the company file: If the company file is stored in a read-only network folder, you need to move it to a folder with full permissions. You can create a new folder on your desktop and move the company file to it.

4. Disable multi-user access: If the file is being accessed by multiple users, you can disable multi-user access to resolve the error. Go to the "File" menu in QuickBooks and select "Utilities". Click on "Stop hosting multi-user access" to disable multi-user access.

5. Use the QuickBooks File Doctor: If none of the above solutions work, you can use the QuickBooks File Doctor to diagnose and fix the issue. This tool is available on the QuickBooks website and can help resolve a wide range of QuickBooks errors.

By following these steps, you should be able to resolve the QuickBooks Error Code 12, 0 and access your company file without any issues.

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