The government probably hoped that a reduced charge of €5 before Sept 28th would encourage people to register their septic tanks and other waste treatment systems. It seems that only 18000 people had registered their waste treatment systems online by the end of August 2012 . There are about half a million homes that are not connected to the main sewerage system – and if they don’t register before the 28th Sept the fee will rise to €50.
The deadline for registration is February 1st 2013 .
More here about Septic Tank Registration