The Commission for Regulation of Utilities says bills will not be issued until July 1st next year
Solidarity TD Paul Murphy claims plans to introduce excess water charges from January 2019 "will face mass opposition from people".
Irish Water has confirmed plans are in place to introduce the charges from next January.
A spokesperson says "the clock will start" on excess charging from next year.
A new report from the Commission for Regulation of Utilities (CRU) also confirms the suspension of water charges will continue until December 31st 2018.
The CRU says there will be no charges to domestic customers in any circumstances.
But it also says excess use charges will not begin until January 1st 2019 "at the earliest."
While bills for excess use charges will not be issued until July 1st next year "at the earliest."
The rules and processes relating to excess use charges will be determined by the Housing Minister, Eoghan Murphy.
However Irish Water says a public consultation is to be carried out to determine what constitutes excess usage.
In a statement, Irish Water says: "The Water Charges Plan clarifies that there will be no charges for water services for domestic customers in 2018; provides that excess use charges will apply from 2019; advises that detail regarding excess use charge levels, commencement dates and associated rules and processes will be agreed with the Minister and the CRU and provided in a later version of the Water Charges Plan".
"Irish Water will implement this Government policy as directed and sees the policy on charging for excess usage as primarily a policy that will enable us to assist customers to conserve water and fix leaks."
Statement from Irish Water: pic.twitter.com/p8Yg4bBH6R— Jack Quann (@jqbilbao) February 9, 2018
The Water Services Act 2017 says that charges to domestic customers will only apply in cases where the volume of water services consumed exceeds the 213,000 litres annual threshold amount.
The CRU says an 'allowance amount' means a 25,000 litres per year allowance, additional to the threshold amount, for each additional person above four in a premises.
The threshold and allowance amounts will take effect on and from January 1st 2018, although consumption in 2018 will "never be subject to excess use charges".
Therefore, the CRU says, Irish Water domestic customers will not be liable for charges until January 1st 2019 at the earliest.
It adds: "Irish Water will not issue bills for water services provided to a dwelling above the threshold amount before 1st July 2019, and these bills will cover a period commencing January 1st 2019 at the earliest".
The report also outlines what Irish Water will charge for.
It will issue charges for water supply, wastewater supply and 'other service charges' - such as connection services, or if a customer asks the utility to carry out additional services.
This could include services such as a special meter reading, priced at €17, or a meter testing for €100.
Solidarity TD Paul Murphy has claimed the plans are unenforceable.
He said: "The news that Irish Water plans to charge for water from January 1st 2019 will come as no surprise to those following the debates in the Dáil.
"This attempted re-introduction is the fruit of Fianna Fáil's betrayal of its election promise.
"Clearly, any excessive usage charges would only be the thin edge of the wedge in attempting to re-introduce water charges for all.
"However, there is a world of difference between Irish Water's plan for charges and their actual implementation.
"Water charges remain politically completely toxic.
"The Government, facing into local, European and possibly a general election in 2019, would be making a serious political error if it actually tried to implement these hated charges.
"It should recall that they were partially responsible for the almost complete wipe-out of the Labour Party.
"If they do proceed with re-introducing charges, they will be unable to implement them in reality.
"They will face mass opposition from people who after waging a successful campaign of non-payment and mass protest to defeat water charges won't accept them being brought in through the backdoor.
"What's more, Irish Water would face an immense obstacle in the fact that 40% of homes in the State do not have meters and therefore cannot be charged."
The Department of Housing, Planning and Local Government had yet to respond to queries at the original time of publication.
Read the full Irish Water Charges Plan here