The 90 day trial period, which was first introduced in 2009 for employers with less than 20 employees and amended in April 2011 to apply to all employers, has to be agreed on between employer and employee before the employment relationship commences – not after. And agreement means that it has to be fixed in writing and that the employee has to be given enough time to consider it.
Seems logical, however in Blackmore v Honick Properties Limited  NZEmpC 152, the employer got it all wrong. The letter of offer did not include a reference to a trial period and no agreement was reached on a trial period before the commencement of the employment relationship. On Mr Blackmore’s first day he was given an employment agreement to sign, which included the trial period. He signed the agreement, but when he later got dismissed at the end of the trial period, he lodged a PG for unjustified dismissal.
The Court held that the trial period was invalid as he was already an employee when he signed the agreement.
Sometimes a Court just has to explain the obvious.