Client Diary has very good options in the reports to whether to include tax or not include tax in the reports.
On how to do this with the reports go to
On how to generate reports in Client Diary Click Here
Here are some examples below of what the reports look like when those options are selected.
Their is an option in Employee Security Groups where you can make it that only employees with all access can do the tax option in the reports instead of all employees by selecting or unselecting Change Tax Options (Inc/Exc). Click Here on how to set this up in your Client Diary.