InternetNZ - the non-profit that administers the .nz domain (or local website and email addresses) - is increasing its wholesale fees from $1.25 to $1.50 a month from June 1.
ISPs and others who sell domain names are expected to pass on the increase.
"Falling registrations are threatening our ability to offer the core security and co-ordination services which our market demands. In order to sustainably offer those vital services long term, we have to increase our prices," InternetNZ chief executive Jordan Carter said.
InternetNZ now faces competition from the private .kiwi and, more broadly, from the trend that sees people or companies setting up a page on Facebook rather than creating their own website - putting an end to years of steep growth in registrations.
InternetNZ now knows the real size of the local market, Carter said.
"Since we started it's been all about growth. We can now see how big our market really is and with this change, maintain our organisation at the right size to service that market, as well as delivering on our public good commitments."
Carter described the increase as modest and well overdue.
InternetNZ's most recently published accounts are for the 12 months to March 31, 2018.
They show the non-profit making a surplus of $867,051, up from 2017's $772,358.
Operating revenue - generated almost entirely from wholesale domain fees - increased to $10.7m from the $10.2m reported in 2017. It was topped up by $658,560 in investment activity revenue.
Expenses, which included advocacy work and community and research grants, increased from $10.0m to $10.5m.
Carter oversaw a restructure in 2018 that saw InternetNZ merge with its NZ Registry Services subsidiary, while the board of the Domain Name Commission or DNC - which among other things referees disputes over web addresses - was slimmed down.
And although it faces apparent falling registration revenue (its 2019 accounts won't be posted until July), life is getting more complicated for the InternetNZ.
Last year was a complicated one for the non-profit organisation, as it grappled with fallout from the Christchurch shootings.
In April, InternetNZ said it had put "emergency measures" in place that "lock" a local website address with harmful content if need be.
Carter later said although his organisation had the ability to make content inaccessible, he didn't want to play sheriff.
The Government needed to clarify if the Chief Censor, Police or another agency - or combination of agencies - should make a call about which content to block, and when.
