Hundreds of Wairarapa property owners have been warned the final sign-off for building work they have completed is years overdue.
Masterton District Council has written to 640 owners who got a building consent but never got a code compliance certificate (CCC).
These dated as far back as 1992, and most were prior to 2015.
The owners have been told the council was refusing to issue CCC compliance "at this time".
However, a certificate for old work could still be issued, if it was modified according to how long the materials were expected to last, the council said in a statement.
"A number of CCCs have already been issued to owners who have received letters and made contact with the council."
One recipient of the council's letter has lodged an anonymous complaint with the Ministry of Business, Innovation and Employment accusing the council of acting illegally, which they also sent to RNZ.
"MDC has made unlawful decisions to refuse to issue CCC," the complaint said.
It cited the Building Act that requires a council tell a property owner they must get compliance within 20 days of the two-year anniversary of the building consent being issued.
The ministry said it would make a decision on this complaint by next Monday.
A business owner who declined to be identified said the council was doing what it could to tidy up its building control records, given the challenges of a lot of construction in Wairarapa and a high turnover of staff in the building control unit in the last couple of years.
The problem of consents lingering without CCCs being issued was "common" among councils nationwide, the district council said.
An audit of the council by the ministry showed it was addressing the CCC problem.
The council wrote to people 10 months after the date of a consent warning that unless work had started there was a risk the consent would lapse (work must start within 12 months of a consent being issued).
It also sent out a letter after 21 months reminding them they needed to apply for a CCC and at 24 months, refusing a CCC if one had not been applied for.