Inland Revenue (IRD) says it is honing in on customers who are not declaring income from cryptocurrencies in their tax returns.

Cryptocurrencies are treated as a form of property for tax purposes, and what people make from selling, trading or exchanging them is taxable.

Spokesperson Trevor Jeffries said IRD had identified 227,000 cryptocurrency users in New Zealand who had made about 7 million transactions with a value of $7.8 billion in the last tax year.

"We want customers and tax agents to know that we are stepping up our compliance activities for customers with cryptoassets," he said.

"Despite popular thinking - people are not invisible on blockchain, and we have the tools and the analytics capabilities to identify and expose cryptoasset activities."

He said IRD had signed up to the cryptoasset reporting framework, which meant it would get more data on customers' transactions outside New Zealand.