Ernst & Young reveals data breach after hack on support system

Ernst & Young confirms breach via third-party IT service management platform exposing client tax data between March 28 and April 12, 2026
Attackers gained access to documents linked to tax relief tickets; the exact scope and affected clients remain undisclosed with no dark web leaks or group claims for now
EY activated incident response, secured systems and offers 24 months of Experian identity monitoring to affected clients

Ernst & Young (EY) has confirmed that it suffered a cyber attack in which it lost sensitive client information, including tax data.

In a data breach notification letter sent to affected individuals, the company said that on April 23, 2026, it detected “abnormal activity” on a third-party platform used by its IT team. This is an IT service management platform that helps EY staff support the teams that perform tax-related work for clients. Therefore, the tickets submitted through this platform sometimes also contain documents with client tax information that may have been disclosed in the incident.

EY then activated its incident response protocols and brought in third-party cybersecurity experts, as well as notifying relevant authorities and affected clients.

Free identity theft protection

Further investigation revealed that the unnamed threat actors broke in on March 28, 2026 and until April 12 have exfiltrated the files. EY did not say exactly what information was pulled or how many clients were affected. We also don’t know if this only applies to US customers, or overseas as well. The attackers have since been removed from EY’s virtual premises and the systems are secured, the company confirmed.

So far, no hacker group has claimed responsibility for this attack, and the data has yet to appear anywhere on the dark web. EY clients should be on the lookout for unsolicited emails, especially those claiming to be from the professional services giant.

To help them stay secure, EY offers 24 months of free identity monitoring and recovery services through Experian.

Ernst & Young is one of the “big four” largest professional service and accounting networks in the world. It is headquartered in London but operates as a global network of independent members spanning more than 150 countries and employing more than 400,000 people. The company’s core business includes insurance, tax, consulting and M&A strategy.

Via Bleeping Computer