Let us suit our trac environment to accomodate custom fields which are useful in reports. I added two fields billable activity which is a checkbox and estimated effort in man days which is textbox.
To do this we edit the trac.ini in the project/conf folder
#vim /trac/project/conf/trac.ini
We add the following lines.

[ticket-custom]

billable = checkbox
billable.label = Billable Activity
billable.value = [...]