Web TimeSheet can integrate only with MS Project and QuickBooks.
However, data can be transferred from Web TimeSheet to any application which can import data in .CSV for .XML format.
Specific reports in Web TimeSheet can be configured to export .CSV files to ADP and Peach tree.
For applications like Simply accounting or Paychex, data can be exported in .CSV format from Web TimeSheet, if the application allows import of .csv files.

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What are the differences between CSV and XLS (Excel) file formats?