There has been a last-minute surge in the number of homeowners submitting property tax returns.
But despite this a large numbers of filings have yet to be submitted.
Revenue said it was extending the deadline as it understands the revaluation and filing process can cause uncertainty for some property owners.
The tax authority denied there were any new problems today with its Local Property Tax (LPT) portal.
Some homeowners had reported problems with the system last week.
Owners are required to revalue their properties for the first time since 2021.
“The extended deadline aims to provide additional time to meet obligations,” Revenue said.
The deadline for homeowners to tell Revenue what they have assessed the value of their homes had been midnight tonight.
By this deadline, property owners also had to tell the tax authority how they intend to pay the tax from next year.
Now they have until the middle of next week to do this.
Owners had to self-assess the value of their property as of last Saturday.
Homeowners have been required to submit a revaluation of their properties for the first time since 2021.
By this afternoon, some 1.4 million local property tax (LPT) returns have been filed, Revenue said.
“The total number of returns to be filed is 2,111,273”, that tax body said.
This means filings in respect of around 700,000 properties have yet to be submitted.
And Revenue is also extending the operation hours for its telephone helplines.
On Monday phone lines will be open between 9am and 8pm, instead of between 9.30am and 4.30pm.
The same times will apply for the phone lines on Tuesday.
On Wednesday, the phone line will be open between 9am and 4.30.
The helpline is on 01 738 3626.
If anyone is experiencing any difficulties using the LPT portal or filing ar return, they can call the RevenueLPT helpline, the tax authority said.
Some people have been surprised that they have moved up a valuation band, despite the bands being widened for the new valuations to avoid people being hit hard much higher LPT amounts.
Residential property values have jumped by 36pc since the last valuation exercise for the property tax four years ago.
Revenue said the new valuations would apply for the Local Property Tax from next year. The tax is a self-assessment charge.
And a large number of local authorities have used the discretion afforded to them to increase the charge in their area by the maximum 15pc.
Revenue warned property owners that the valuation they can get for their home on its website is a guide only.
Revenue has said there are various payment options.
Owners can pay in full, by credit or debit card or cash through a payment service provider, such as An Post or Payzone.
The deadline for those who choose this payment deadline is Friday, January 9, next.
Monthly direct debits will have the first payment processed from Thursday, January 15 next.
Deduction at source, from salary, wages or occupational pension, will start to be processed in January.