The Employment Relations Authority last year ordered Bernadine Hull to repay $103,378 she stole from the Papakura East Medical Centre between 2007 and 2012.
She was caught on a camera, installed in secret, taking an envelope of money from the office.
Ms Hull claimed she took it home and lost it.
Employment law expert Kathryn Beck says such filming was okay when bosses suspected their staff of wrongdoing, so long as it didn't go too far.
Ms Beck, a partner at Auckland employment law firm SBM Legal, said secret surveillance was becoming more widespread at workplaces.
"If you're an employer and you're wanting to do that if you need to or as part of normal practice, I would say you should have that in a policy saying you reserve the right to use CCTV covert surveillance if and when it's necessary, and if you use it you've given people due warning," she said.
"[Without a policy], if it's for a lawful purpose and if you don't go any further then you need to then you're probably going to be okay."
Filming suspected wrongdoing should be fine if it was not done in areas, such as bathrooms or changing rooms, where there was an expectation of privacy.
It was also legitimate if seeking information from the person would impact on an investigation, giving the employee a heads-up their boss was on to them, Ms Beck said.
Covert surveillance should also stop once evidence was gathered.
"You can't just keep recording. It's all about what's reasonable."
Some firms would have cameras operating above the cash register for security reasons and they might also catch out dishonest employees.
New Zealand's privacy principles say someone should be told when information about them is collected, although there are exceptions.
- NZME
