HOMEOWNERS who refused to register for the property tax will not be hit with an interest charge when the money is automatically deducted from their salaries, pensions or bank accounts on July 1.
Some 210,000 people have yet to register despite a late surge yesterday where 10,000 filed a return every hour.
However, they have been given extra time to file with the deadline extended by 20 hours to 8pm tonight.
It was extended because of an "unprecedented volume of calls" to the helpline, with 30,000 calls received by 5.30pm last night.
Of those, 8,000 wanted to file their return over the phone.
However, despite a large number of returns still outstanding, the Revenue Commissioners revealed that many of these will not be penalised despite refusing to sign up for the controversial tax.
Only in cases where it could not deduct the tax would late-payment penalties be applied, it said.
This is despite repeated warnings to 1.66 million liable homeowners to register by midnight yesterday or face the prospect of an 8pc interest charge on the amount due.
The Revenue Commissioners said the penalty would not be imposed because they could access and deduct the money and so the charge would be considered to be paid on time.
Only in cases where a source of income could not be identified would the interest be applied, and then only following correspondence.
"Interest charges at 8pc per annum apply to late payment of LPT (local property tax) and penalties may also arise," a spokeswoman said.
"If a person does not file a return, the amount set out in the Revenue estimate will be collected through deduction at source and will not attract interest.
"This is because we'll have the money on time.
"If, for whatever reason, we cannot deduct at source then interest will be applied.
"Penalties will not be imposed automatically and will be preceded by engagement with the taxpayer.
"Any general imposition of interest will be well flagged in advance.
Callers to the Revenue helpline at 1890 200 255 were left waiting for an average of two minutes due to the sheer volume of calls yesterday.
Up to 400 staff will begin collecting the property tax from July.
The Government has allocated almost €26m this year to put in place the systems needed to ensure compliance.
The first wave of households who refuse to pay will be PAYE workers, and the money will be taken directly from pay packets or attachment of bank accounts.
Deductions can also be taken from state payments or pensions, or referring the debt to a sheriff or solicitor for collection.
Tax refunds due may also be withheld. Those who refuse to pay, and who are later identified, will not be allowed avail of extended payment options including monthly direct debit.