Six guided walk operators are under investigation to ensure they have not been gaming the Great Walks hut booking system.
Bookings for the Great Walks are sold on a first-in, first-served basis with tour operators needing to include the full names and details of anyone they book on behalf of.
The Department of Conservation (DOC) said checks were being made to ensure companies had not made incomplete or unauthorised speculative bookings or occupying more than half of Great Walks hut or campsite spaces for clients.
Those companies operate on the Heaphy, Paparoa and Rakiura tracks.
DOC heritage and visitors director Steve Taylor said they were contacted after irregularities in the booking system were picked up.
"Speculative or non-compliant bookings have been a hot topic this year as Great Walks grow in popularity," he said.
"The downside of this popularity does mean that there will be a few people who try to get around the system and that's where DOC's visitor centre and compliance teams come in."
The compliance team worked with DOC visitor centre staff who reviewed all local Great Walk bookings and reported any that looked suspicious, Taylor said.
"If operators are found to be in breach of their concession agreements, they must either update their bookings or have the places cancelled.
"This compliance action is in addition to standard work undertaken each year by visitor centres to check any irregular bookings with the public, operators, school and community groups."
Speculative bookings are a relatively uncommon issue.
"Compliance action has only been necessary with six operators whose bookings equate to roughly 0.2 percent of Great Walk hut and campsite spaces across the coming season," Taylor said.
"However, where it does occur, we have systems in place to identify and respond to it.
"Peak season dates on the Great Walks can book out fast and it's important access is equal for everyone. Anyone who abuses the system does so to the detriment of the public and the vast majority of concessionaires and agents, who offer an important service on these walks and play by the rules.
He urged people who suspect a business on the Great Walks may not be operating inside the rules to alert the local DOC visitor centre.
DOC's opening day bookings data showed that public or independent bookings made up 93 percent of total bed nights booked with concessionaires representing about 4 percent of bookings and school or community groups filling the rest.