"My resignation as premier could not happen at a worse time, but the timing is completely outside of my control as the ICAC has chosen to take this action during the most challenging weeks of the most challenging times in the history of NSW."
The ICAC is investigating conduct by Ms Berejiklian in the six years until 2018 that "constituted or involved a breach of public trust by exercising public functions" relating to her public role as treasurer and premier, and her private, personal relationship with former MP Daryl Maguire.
In particular, the inquiry will examine the awarding of grant funding to the Australian Clay Target Association Inc in 2016/2017 and the Riverina Conservatorium of Music in Wagga Wagga in 2018.
As part of the ICAC's investigation, a public inquiry is scheduled for 10 October and is expected to last about 10 days.
When is Gladys Berejiklian formally resigning?
Ms Berejiklian said her resignation will take effect "as soon as the NSW Liberal party can elect a new parliamentary leader.”
Who will become the new leader is expected to be decided on Tuesday when the Liberals will hold a party room meeting.
But no formal date has yet been set for Ms Berejiklian's official exit from state parliament as an MP.
She said that date will be determined after consultation with the NSW Electoral Commission on appropriate timing for a by-election, given COVID-19 restrictions.
Ms Berejiklian said the process would "allow the new leader and government a fresh start".
Professor of constitutional law Anne Twomey at the University of Sydney said there will be implications for the government's majority in the state parliament when it sits on 12 October.
"When that happens, when she does resign, that leads to further questions to what might happen in parliament," she told the ABC.
"The government's majority in parliament is extremely slim. There are issues about what happens when she has resigned her seat and they are one down in the House, whether or not a vote of no-confidence might be passed... (We need to observe) the fairly remote possibility of an early election, if there was a vote of no confidence."
"I expect in the circumstances that nobody wants an early election, not even the Labor party at this stage."
When is the party room vote to decide on Ms Berejiklian's successor?
NSW Nationals leader and Deputy NSW Premier John Barilaro has become acting premier until the next NSW Liberal Party leader is determined.
"Any speculation regarding Liberal Party leadership remains an issue for the Liberal Party," Mr Barilaro said in a statement. "The NSW Nationals remain committed to a strong and stable NSW Coalition Government."
The party is set to hold a meeting on Tuesday.
Ms Berejiklian said it was important for her to announce her resignation to provide certainty to voters "during these challenging times of the pandemic".
"I cannot predict how long it will take the ICAC to complete this investigation, let alone deliver a report, in circumstances where I was first called to give evidence at a public hearing nearly 12 months ago," she said on Friday.
Who are the contenders to succeed Ms Berejiklian?
Planning Minister Rob Stokes has indicated he will put his name forward to be the next party leader and premier of the state. Mr Stokes ran against Ms Berejiklian when she assumed the role of premier in 2017, following the resignation of Mike Baird. Considered a party moderate, he has demonstrated an ability to work with the party's centre-right factions.
NSW Treasurer Dominic Perrottet is expected to also nominate himself for the top job. He took on the role as deputy leader and treasurer in 2017. His visibility has grown during the state government's handling of the pandemic.
A crisis cabinet meeting held on Friday afternoon will be one gauge of which MP has the highest number of supporters to lead the party.
What are the pressing issues facing the new premier?
The new premier will be assuming the role during a crucial point in the state's roadmap out of lockdown with 11 October set as the date for the first stage of re-opening.
The re-opening of domestic and international borders will also prominently feature NSW as the first state to implement the changes.
From November, Australian jurisdictions will begin opening up to international travel.
The timetable will depend on vaccination coverage and the outcome of the pilot home quarantine programs.
Gladys Berejiklian previously said the state government aims to welcome home some of the 45,000 Australians stranded abroad with increased activity at Sydney Airport when the state hits the 80 per cent double dose milestone on 25 October.
The new leader will also come into the role as NSW monitors the health system for an expected October peak in COVID-19 hospitalisations and deaths forecast in modelling commissioned by the state government.
NSW recorded 864 local COVID-19 cases and 15 deaths on Friday.
There are currently 1,055 COVID-19 patients in hospital with 210 people in intensive care.
Since the latest outbreak started on 16 June 2021, there have been 352 COVID-19 related deaths and 57,357 locally acquired cases reported.