A total of 9,800 sickness beneficiaries medically assessed as being able to work part time are obliged to look for work as from Monday.
Minister of Social Development Paula Bennett says there is no penalty if people can't find work.
She says those assessed as able to work 15 to 29 hours a week now need to: be available for suitable part-time employment, accept any suitable offers, attend interviews and undertake employment-related training, work experience and work assessments.
Ms Bennett says, under the Government's Future Focus initiative, sickness beneficiaries are also required to get an extra medical reassessment eight weeks after going onto the benefit.
She says that is on top of providing a medical certificates after four weeks on benefit, and then every 13 weeks, to prove eligibility.
They will also have a compulsory review by their case manager if they have been on a sickness benefit for more than 12 months.
There were 59-thousand working age people on the sickness benefits as at April 2011.