Now that the date has been set for the referendum that will allow us to repeal the 8th, the deadline is also set for the Supplement to the Register of Electors.
Any additions or amendments to the supplement must be made more than 14 days before an election (excluding Sundays and holidays). In the case of the referendum on the 25th of May, this means you MUST have submitted the form by the 8th of May at the very latest. Ideally as soon as possible.
Registering requires form RFA 2 available here.
Change of address from that you are already registered under requires form RFA 3 available here.
Now that the date is set, if you are still 17 but will be 18 on or before the 25th of May you may register now, using form RFA 2 above. It is advisable to include a photocopy of your birth certificate.
This also means that if you are going to need a postal vote and are not yet registered for one, you must register by the 27th of April.
If you require a postal vote due to physical disability or illness you need form PVS 1 available here.
If you require a postal vote due to circumstances related to your occupation (which includes some students) you need form PVS 2 available here. Check with your employer or institution to be sure you are eligible.
Postal votes are only available within the country, except for some cases where you are abroad on State business (military, Garda or diplomatic service).