Hello there, @pjvet.

I appreciate you for seeking updates and getting back to us here on the Community page. I'm here to share additional information about the To-Do tasks in QuickBooks Desktop.

For most customers, updating QuickBooks Desktop to the latest release and uninstalling Microsoft SQL Server resolves the issue. On the other hand, have an ongoing investigation about customers having issues adding contacts to a vendor/customer and saving the To-Do list in QuickBooks. That said, our engineers are now working for an immediate fix of this error.

For now, you can update your QuickBooks Desktop and do the verify and rebuild process to fix data issues within your company file. Then, you can reach out to our Support Team and have them add your account to the list of affected users from this investigation (INV-46267). Once added, you'll automatically receive notifications of the latest updates.

Whenever you're free, you may also spare your time reading our help articles as additional guides while working with QuickBooks.

Please extend your patience while we're working for the permanent resolution on this feature. Don't hesitate to drop me a line if you have other QuickBooks questions. Have a good one!