The long-anticipated departure of Trade Minister Tim Groser to become Ambassador to the United States will be announced today, although his actual resignation may be delayed until February, giving him the chance to sign the Trans Pacific Partnership agreement he has spent the past seven years overseeing.
Mr Groser's Trade portfolio is expected to go to Todd McClay.
Inland Revenue is expected to go to Commerce Minister Paul Goldsmith. Speculation on Radio New Zealand that Foreign Minister Murray McCully could be returned to the back bench after an illness is wrong. Mr Key is expecting him to return to work and his portfolio in the New Year.
Ms Collins held both the Corrections and Police portfolios in the first term of the National Government.
She resigned from the Justice portfolio during the 2014 election campaign when emails stolen from blogger Cameron Slater implicated her in a campaign to undermine the position of former Serious Fraud Office head Adam Feeley.
Ms Collins was cleared in an inquiry by retired High Court judge Lest Chisholm more than a year ago - after Mr Key had picked his third-term Cabinet.
This is his first reshuffle since then.
Ms Collins survived a prolonged controversy earlier last year for helping the Oravida firm in China associated with her husband, but before that she was one of Mr Key's best-performing ministers for almost two terms.
She knocked Corrections into shape in the first term of the National Government. Anne Tolley had it in the second term.
Mr Key indicated this morning that his reshuffle would be "minor". That suggests there will be another one part-way through the year.
MPs tipped for promotion this term include first-termer and Act leader David Seymour, Mark Mitchell, the foreign affairs select committee chair, and Alfred Ngaro, the chairman of the social services select committee.
Choosing to reshuffle early will give Mr Key a better summer break and give new ministers a chance to get up to speed on their new portfolios.
Collins' year outside Cabinet
August 2014: Resigns from Cabinet following email leaks alleging she had undermined the head of the Serious Fraud Office Adam Feeley.
September 2014: Re-elected in Papakura seat with 5000-vote majority. Left off the "Roll of Honourables" while an inquiry into the Feeley case is ongoing.
November 2014: Cleared of wrongdoing by an inquiry into the Feeley case, retains use of "Honourable" title.
April 2015: Using her Sunday Star-Times newspaper column, she slams proposals to allocate water rights to iwi.
May 2015: Collins causes trouble from the backbench, as she is thought to be among several caucus members seeking changes to health and safety reforms. The legislation is delayed as a result.
September 2015: Leads calls for singer Chris Brown to be denied entry to NZ because of his assault convictions, saying he should "bugger off". Brown's visa is later denied and his show cancelled.
October 2015: Defends sponsorship deal with an Auckland car dealership - within the rules for a for an MP but not for a minister.
December 7, 2015: Expected to return to Cabinet.
Collins: Her high and lows
2002: Enters Parliament in the Clevedon seat. While in Opposition, she takes on justice and tourism roles before being promoted to social welfare spokeswoman following the demotion of Katherine Rich.
2005: After strong performances in Opposition, Collins jumps from 48th to 12th on National's list and is re-elected in Clevedon.
2008: Wins National Party nomination for Papakura electorate after boundaries are redrawn, and then wins the seat at the general election with a 10,000-vote majority. In National's new government she is given police, corrections, and veterans' affairs portfolios.
2009: Collins announces 600 extra frontline police and earns the nickname "Crusher Collins" after introducing legislation to crush the cars of boy racers. She also oversees a nationwide rollout of tasers.
2010: Reintroduces private prisons, beginning with Mt Eden Correctional Facility.
2011: Rises to 5th in National list, and highest-ranked woman in Parliament. After the 2011 election she is appointed Minister of Justice, ACC, and Ethnic Affairs. She leads an overhaul of ACC following a massive privacy breach of 6700 claimants' details to claimant Bronwyn Pullar.
May 2012: Takes defamation action against Labour MPs Trevor Mallard and Andrew Little after they link her to the leak of an email about Pullar's case.
December 2012: Passes major alcohol law reforms, after significantly cutting back on original proposals by her predecessor Simon Power such as restrictions on "alcopops".
Collins also slams a report by retired Canadian Supreme Court Judge Ian Binnie which had recommended compensation for David Bain. Her actions prompt High Court action by the Bain camp.
October 2013: In what later becomes known as the Oravida scandal, Collins has dinner with bosses of the New Zealand milk company, of which her husband is a director, while on a taxpayer-funded trip to China.
March 2014: Details of the Oravida dinner emerge. Labour calls for her to resign because of a conflict of interest. The case rolls on for weeks and Prime Minister John Key puts her on a "final warning" but Collins gets away with an apology.
May 2014: Upset at the ministerial resignation of close friend Maurice Williamson, Collins lashes out at TVNZ reporter Katie Bradford. She apologises and takes some time off.
August 2014: Nicky Hager's book Dirty Politics reveals Collins passed private information about a public servant to blogger Cameron Slater. Prime Minister John Key puts her on notice. She later resigns from Cabinet following email leaks alleging she had undermined the head of the Serious Fraud Office Adam Feeley.
September 2014: Re-elected in Papakura seat with 5000-vote majority. Left off the "Roll of Honourables" while an inquiry into the Feeley case is ongoing.
November 2014: Cleared of wrongdoing by an inquiry into her actions in the Feeley case, retains use of "Honourable" title.
April 2015: Using her Sunday Star-Times newspaper column, she slams proposals to allocate water rights to iwi.
May 2015: Collins causes trouble from the backbenches, as she is thought to be among several caucus members seeking changes to health and safety reforms. The legislation is delayed as a result.
June 2015: Leads calls for singer Chris Brown to be denied entry to NZ because of his assault convictions, saying he should "bugger off". Brown's visa is later denied and his shows are cancelled.
October 2015: Defends sponsorship deal with an Auckland car dealership - within the rules for a for an MP but not for a minister.
December 7, 2015: Expected to be returned to Cabinet.
