New Zealand's top lawyers have awoken to a new title as the death of the monarch means the Queen's Counsel title has been converted to King's Counsel.

A statement to the legal profession from Chief Justice Helen Winkelmann issued on Friday morning said QCs are now KCs following the death of the Queen.

Criminal cases also become "The King v X" and senior court announcements change to refer to "the King's Judge(s)," the statement said.

"It was with sadness that I woke to the news that Her Majesty Queen Elizabeth II has died," Winkelmann's statement said.

"On behalf of the judiciary I have issued a statement of condolence recognising her life of
extraordinary commitment to duty and unprecedented service as Sovereign."

Courthouse flags will fly at half-mast and a decision was made to keep courts open today, the statement said.

"The judiciary has a plan in place for this day, and I write to advise you of it now.

"Judges have been invited to mark the event in court in a manner of their own choosing – for example with a short statement of condolence, a karakia that has been prepared to mark this event, or two minutes silence."

All changes are effective as of today.

"As a matter of law and constitutional practice, the Crown is never vacant," the statement said.

"The new monarch accedes to the throne immediately upon the death of his or her predecessor."

The Governor-General appoints QCs / KCs from the ranks of lawyers "in recognition of their extraordinary contributions to the field of law", according to the NZ Bar association.

The awarding of the title, informally known as "taking silk", carries huge prestige and allows barristers to command significantly higher fees.

From 2007 to 2009, the title of QC was briefly abolished, being replaced by "Senior Counsel".

In 2009, Attorney-General Christopher Finlayson, himself now a KC, announced the new Key Government was restoring the QC title.