If you are selling your house, you will need to have your septic system inspected.  The inspection report is a 17 page packet that describes the current condition of your septic system.  Do not leave this to the last minute.  The last thing that you need when you are selling is an additional last minute panic when you have a deadline for the passing and the report is not done.  The report is good for 2 years and you could stretch it to 3 years of you pump the septic tank each year.  Some people have an unofficial inspection done just to see how well it is functioning.  The cost is the same, but no report is sent to the Board of Health.  One of the major problems that septic systems have is when the solids from the septic tank enter the soil absorption system.  A filter in the tank along with regular maintenance will dramatically minimize this problem.