Councils estimate they have yet to identify 10,000 buildings nationwide that are earthquake-prone and need upgrading or demolition.
About 700 of those must be identified in high-risk seismic zones by the first deadline of 1 January.
The figures come from the first update in months from the Ministry of Business, Innovation and Employment about implementing the earthquake-prone building laws.
About half of the 38 councils in high-risk zones are "not confident" or only "somewhat confident" of meeting all the deadlines for priority seismic work.
However, 36 of the 38 councils believe they can identify all their priority buildings by 1 January.
"Confidence is high that the first deadlines for identification will be met," the ministry said, after analysing reports from 62 councils.
So far, 283 buildings in high seismic-risk areas of 10 districts have been strengthened or demolished, and another 65 buildings in medium-risk zones.
Of the 37 councils in medium-risk areas, a third have identified all potentially priority earthquake-prone buildings, and all expect to have done this by mid-2022.
Building owners who were alerted by councils in 2018-19 to take action now face having to get 1200 engineering assessments done.
In the past 12 months, 331 buildings in high-risk zones were assessed as earthquake prone and 1264 not.
However, councils recorded concerns about "the accuracy, quality and timeliness of engineering assessments" revolving around a lack of information from engineers, including how they justified their assessment.
Overall, the ministry expected engineeers to assess 10,300 buildings in the next eight years, resulting in 4100 of those being added to the earthquake-prone building register.
"Some territorial authorities noted a shortage of qualified engineers, while others noted that engineers' reports were being provided within the time (12 months) expected."
In high-risk zones, about half of the councils have consulted with communities about what routes should be classed as particularly busy, along which the toughest deadlines to do up or demolish buildings - or just 7.5 years - would apply. Half of councils have chosen not to designate any routes as busy or strategic.
The ministry has also been evaluating the new national system for managing quake-prone buildings, and expects to wrap up that work next month. Most councils have now removed local policies to fit with the national approach.
Apartment owners in Wellington have petitioned Parliament asking the government to provide financial and technical help to residents facing "significant financial costs and personal stress to comply with the current earthquake-prone building legislation".
They are warning buildings will not be strengthened unless the government intervenes.