Symptoms:
When transferring 'Client Invoice' from Web Timesheet to QuickBooks, the following error message occurs and does not transfer time information. In some case, although this error comes up, the expenses will get transferred but not the time information.

"The name of the list item is already in use."

Cause:
This issue can occur when following mapping is done and the Project Name length is more than 31 characters,

Project Name –> Jobs for Expenses
Project Name –> Items for Time entries

Any QuickBooks Desktop version (From 2006 and above) , will support Job Name length upto 31 characters (including spaces) and Item Name length  upto 41 characters (including spaces). If the Project Name falls between these two length, then Expenses will get transferred but Time entries will not get transferred.

Resolution:
Ensure that the name of the project has less than 31 characters in Web TimeSheet.