Nelson Marlborough DHB charges $90 for the certificates, with two-thirds kept by the DHB, while in the Southern and Lakes DHBs, the doctors keep the fee themselves, Fairfax reported.
MidCentral DHB charges $70, with the money going towards "social events".
Several large DHBs have stopped charging for the certificates, including Capital & Coast, Auckland, Counties Manukau, and Waikato.
DHBs are now also looking to scrap the fee, following inquiries by the Dominion Post.
The newspaper has obtained an email from Deborah Powell, national secretary of the Resident Doctors' Association, advising regional representatives to end the practice.
"We have been approached by the DHBs who ... have received an [Official Information Act] request from the media concerning the payment of what is colloquially termed ash cash. All the DHBs now wish to stop payment," she wrote.
- nzherald.co.nz