In 50 raids, police in Argentina recovered $5m (£3.6m, €4.7m) in cash from a network including seven tax officials national newspaper La Nacion reported last week.
The tax office employees, said to be in the agency’s IT and systems departments, had been selling the data on since 2010.
According to La Nacion’s sources, ‘major companies and even banks’ paid for the information.
One tax office employee was caught with $20,000 hidden inside tea.
The case highlights the risks involved in common reporting standard (CRS) in which often wealthy taxpayers’ details will be pinged around the world.
Wealth planner and trust expert with financial planners Swisspartners, Cintia Amoros said: “Sadly, Argentina is not ready for information exchange, as many countries are not ready. On the other hand the arrest shows that Argentina is going in the right direction.”
Robert Mack, head of private clients and trusts at law firm HSM Chambers, said: “This was bound to happen. Client data is just another commodity.”
Colin Riegels, partner at law firm Harney Westwood & Riegels, said westerners were “hard wired” to trust in their officials but they could not expect that in much of the world where tax payers need protection from rogue tax officials.