QuickBooks files can get corrupted due to a variety of reasons. This includes having file size limits that are too large, or malicious attacks from viruses and malware. If QuickBooks is used in a multi-user environment and the company file is primarily stored on the server, dropped-out networks or failed hard drives can cause corruption. Furthermore, third-party applications or software can block access to QuickBooks and outdated versions of QuickBooks can also contribute to file corruption.