OWNERS of about 290,000 sceptic tanks have registered with their local authority.
But at least 110,000 have yet to come forward as the February 1 deadline looms.
Secretary General of the Department of the Environment Geraldine Tallon could not say how many people had registered before the end of September to avail of the reduced fee of €5.
The Dail Public Accounts Committee was also told that 1.1 million people had paid the household charge by November 28.
It is estimated that there are about 1.6 million properties eligible for the charge in the state.
Finance Minister Michael Noonan yesterday announced in the Budget that the charge would be scrapped next year, but would be replaced with a property tax worth 0.18pc on the value of homes up to €1m from the second half of the year.