Note: If you have support from ByWater, they will create these reports for you and save them in your Saved Reports or have them automatically scheduled and emailed to you. Contact your rep or put in a ticket with ByWater to set up reports using the relevant tables below.
Report Information on the Koha Manual
Koha Wiki on Reports
Only staff with the create_reports permission (or the superlibrarian permission) will be able to create custom reports, either with the guided report wizard or directly with SQL.

Relevant Tables
illrequests
koha_plugin_com_theke_innreach_agency_to_patron
koha_plugin_com_theke_innreach_contributed_items
koha_plugin_com_theke_innreach_contributed_biblios
koha_plugin_com_theke_innreach_task_queue
illrequestattributes
In Rapido, it’s these instead of Innreach:
koha_plugin_com_bywatersolutions_rapidoill_task_queue
koha_plugin_com_bywatersolutions_rapidoill_circ_actions
koha_plugin_rapidoill_duplicate_backup
koha_plugin_com_bywatersolutions_rapidoill_agency_to_patron