Workers at the insurance company's asset management division were reportedly stunned to learn in a memo that they had been fired, only to find out later that the note that had mistakenly gone viral was intended for only one employee.
The memo coldly instructed the 1,300 workers to return all company property and to give up their clearance badges and company passwords, The Daily Telegraph reported.
"I am required to remind you of your contractual obligations to the company you are leaving. You have an obligation to retain any confidential information pertaining to Aviva Investors operations, systems and clients," the note said.
The note from the human resources department also thanked the employees for their contributions and wished them "all the best for the future."
The company apologized for the mistake.