The Queenstown Lakes District Council is chasing up 300 property owners who have not heeded its call to register their holiday homes.
Last month, the council sent letters to almost 800 owners of unregistered holiday accommodation, warning them to register before 17 February.
The council said renting out a holiday home all year round could see the residential rates being doubled.
A spokesman, Stewart Burns, said the council would try to contact the 300 owners who were yet to register.
He said maximum penalties for not complying include a fine of up to $300,000, or two years imprisonment.