Local Government Minister Eoghan Murphy has confirmed anyone placed on the draft electoral register in recent months will have to re-apply to vote in the upcoming general election.
The Register of Electors, which will apply to the 2020 General Election on February 8th, is the 2019-2020 register - plus the supplement to that register.
However it will not include those on the draft electoral register.
The polling date means thousands of people placed on the draft register in recent months are not eligible to vote, as the updated register is not valid until February 15th.
While those impacted will still be able to be put on the supplementary register, they would have to register for a second time to guarantee their vote.
Concerns have been raised that the law regarding the register cannot be changed now as the Dáil is to be dissolved.
Minister Murphy said that there is still time to register to vote.
"It is up to each of us as individuals to ensure we are correctly registered to vote and the best way to do that is to check directly with the relevant local authority.
"However, the crucial point today is that there is still time to register to vote in this General Election."
Registering to vote
People can check online if their details are included on the 2019-2020 electoral register.
Alternatively, people can check directly with their local authority.
If their details are included correctly, no further action is necessary.
However if their details are not included, they should contact the relevant local authority where they live and check if their details are included in the supplement to the register.
If their details are included in the supplement to the register of electors no further action is required.
But if they are not included in either the register or the supplement, they should get the appropriate application from their local authority (or download it from checktheregister.ie) and complete the form.
Before signing the declaration, they must bring it with a photo ID to their local Garda station and sign it in the presence of a member of An Garda Síochána.
Forms must reach the local authority on or before close of business on January 22nd in order for people to be registered for this election.
People must call to the local authority to register, or send it by post.
It comes as the Government approved draft legislation for reforms to the electoral registration process.
A rolling register will replace the system of register and supplement.
The changes to identity verification and online registration, currently being piloted in Dublin, will see a more streamlined application process that will mean most people never have to go to a Garda station.
But Minister Murphy added: "While I appreciate that this is of little comfort to those who may be inconvenienced in registering for this election, substantial progress has been made towards a modernised process including a significant public consultation campaign and the preparation of outline legislation for reform".
There were earlier calls for the Government to ensure no newly-registered voters were denied the right to vote.