Following the investigation, a spokesman said the ICO was pleased the ABHB was "committed to taking action" to address the problems highlighted by the report.
But Nick Pickles, director of privacy and civil liberties campaign group Big Brother Watch, said ABHB's mistake was not an "isolated one" in the NHS and called for changes to the way data breaches are investigated.
Yesterday, it emerged that ABHB became aware of the breach on March 30 last year - 14 days before the investigation began.
An ICO spokesman added: "ABHB have also signed an undertaking to address the concerns expressed by the ICO." This included ensuring staff were "aware and trained" on the board's policies of collecting and storing patients' personal data as well as introducing a new checking system before people's details were sent out.
"ABHB has confirmed it has already introduced some of these measures," added the spokesman.