The latest figures from Revenue show that one quarter of all relevant households have yet to register.
The deadline for online registrations is midnight tomorrow, May 28th.
Author of "Know Your Rights" Andrew McCann says people are strongly advised to register as the penalties for not doing so are stiff.
"There may be some people who may be quite adamant who say they are not paying; and just to be very clear - in the legislation, it says people can be fined up to 5,000 euro for non-compliance of registration and up to 500 euro per day for non-compliance to correspondence" he said.
"Revenue do have the powers to either issue a sheriff or to remove monies from accounts as needs be " he added.