Inland Revenue reaped nearly $68 million in tax from property speculators over the past three years.
Two thirds of the undeclared cases were in Auckland but both the department and the real estate industry say speculation appears to be waning.
In the year to mid-2011, the department wrapped up 386 cases reaping nearly $34 million but the number of cases has dropped steadily since.
The IRD attributes part of the decline to its efforts in educating property traders about their obligations.
But property investors and the real estate industry say that even in the strong Auckland market, speculators are much less prevalent than they once were.