Less than half of all septic tank owners had paid the registration charge by last night's deadline, to avail of a low-level charge.
Figures from the body tasked with collecting the charge, the Local Government Management Agency, show 230,000 owners had registered their septic tanks.
The deadline for registering septic tanks for the concessionary rate of €5 expired at midnight.
The fee rises to €50 until the deadline of February 2013.
The Local Government Management Agency said the registrations had been received online, by post and in person.
It is estimated that there are between 450,000 and 500,000 septic tanks in the country.