It is an offence to keep a dog in Ireland unless you have a dog licence.
In order to obtain a dog licence in Ireland , you must be over 16 years of age.
Dog licences are issued by your post office or your local authority and at March 2006 cost only €12.70 euro a year or €253.95 for multiple dogs.

All dogs over four months must have a licence. Puppies under four months who are still with their mothers don't require licences but once they leave their mothers they must have a licence.
Your dog must be accompanied by and be under your effective control or the control of another responsible person if it is outside your home or premises or the home or premises of the person in charge of it.

You can be requested by a dog warden to produce evidence of your dog licence and failure to do so can result in an on-the-spot fine of €30.
This isn't much of a penalty - and many dog owners in Ireland don't bother with a licence. Failure to pay a fine within a specified period can result in prosecution by your local authority.

Licences are not required for dogs in the possession of the County Council, the Irish Society for the Prevention of Cruelty to Animals, Gardai, blind persons' guide-dogs, and any dog imported into the State for less than 30 days.
The revenue from dog licences finances the operation of dog control services in local areas throughout the country