Before you solve QuickBooks Error 15311, I will list down various triggers for the error in the application. Here is a list for the same

1. The QB Entries in the Windows registry may be corrupt or damaged.
2. Presence of virus or malware in your computer or QB software/executive files.
3. Important QB files deleted by a third-party program.
4. Corrupt or incomplete installation of QuickBooks accounting software.

Now that you know what is causing QuickBooks Error 15311, you can easily solve the error based on that. But if you need to avail professional help contact QuickBooks Support team.