When upgrading or installing QuickBooks Desktop, the installation error QuickBooks Error 1603 appears. The most common causes include problems with Windows components, incomplete installation files, or a broken Microsoft.NET Framework. When a fatal issue occurs during setup, users could get an error message that stops the operation. Repairing system files and reinstalling are steps in the troubleshooting process. The number to reach a member of our QuickBooks team is 1.855.738.2784.