The Auckland District Health Board is asking immigration officials to make it clearer to visitors they don't get health treatment for free.
The DHB has issued bills worth $11 million over the past decade for visitors who needed medical care.
It says the debt is affecting New Zealanders, who are missing out on care that could have been provided if the funds were available.
The DHB says most debts are paid, but it is still owed hundreds of thousand of dollars most years.
It will write to Immigration New Zealand next week asking it to make it clearer to tourists or those on temporary visas that they must pay for health care.
Immigration New Zealand says sponsors of people with visas confirm their visitor has financial support and may have to pay for medical treatment.
It says the sponsor is responsible for any bills if people end up needing care.
