In Texas they (homeowners w/septic systems) are supposed to have them inspected quarterly or on some schedule. State had/has requirements and they pushed the responsibility down to the counties and related AHJs. Of course there are legacy drain field systems and then the aerobic systems. Official inspections of septic come from the companies who are licensed to install/maintain the systems. There are courses offered for a 'septic certification' and many HIs take them and then claim they are the specialists for inspecting the systems ... as if they can see inside the tanks, pump them out, etc., etc.. I do not inspect septics and advise client to have local/authorized septic company provide inspection. Usually there is a list of inspections on a control panel label indicating the recurring inspections by a local company. I advise client to call them for details/history. I do look for tank access lids and stability/security, but that is as far as I go.