Revenue from other DHBs for local treatment of patients from outside Hawke's Bay was $11.5m, down from just over $12m the previous year.
Labour health spokesman David Clark said the inter-DHB funding system needed to be changed.
"It has to be considered in base funding," Dr Clark said.
"My position is that we need a full and broad-ranging review into funding."
The current system disadvantaged smaller DHBs, partially because of extra administrative costs, he added.
Payments from Hawke's Bay DHB to other boards totalled $50.7m in 2014/15.
The board still had a surplus for the most recent financial year due to a number of factors, including increased funding from the Ministry of Health.
National prices for the care of patients from other districts were agreed upon by all DHBs, so the cost for the same treatment should not vary between regions.
A number of specialist services were not available in Hawke's Bay, and patients were required to travel to other centres for these types of care.
"Clearly there are some interventions such as open heart surgery and radiotherapy that need to be undertaken at specialist centres," Mr Evans said.
Most smaller DHBs have been paying more to other boards than they received from them for patient care.
Whanganui DHB chief executive Julie Patterson said last month her region was missing out on revenue due to patients not giving correct addresses.
The Whanganui board received just $7m from other DHBs for its treatment of visitors in the past financial year.
As was the case in Hawke's Bay, the Whanganui DHB sent patients out of its own region for specialist care.
Northland and Bay of Plenty DHBs paid more to other boards than Hawke's Bay did, but both had higher populations.
Mr Evans said it was not possible to provide all types of care in the Hawke's Bay region.
"HBDHB is always looking to provide as much care as close to the patients' home as it can, however it must be both clinically safe and economically viable."
