Inland Revenue is launching a marketing campaign to stop tradespeople from doing cash jobs and not paying tax.
It is specifically targeting those operating in north and south Auckland, specifically Flatbush, Takanini, Silverdale and Albany.
Cash jobs are estimated to cost the IRD billions of dollars of lost revenue each year.
Its group manager of marketing and communications, Andrew Stott, said the campaign would target tradespeople rather than their customers.
Mr Stott said the IRD was working with organisations such as Master Plumbers and Master Builders to encourage tradespeople to keep good books and declare all their income.