Sitting members of parliament are required to publish details of earnings. In the latest update revealed Wednesday, Osborne said of his BlackRock role:
"I expect to be paid 162,500 pounds a quarter in return for a quarterly commitment of 12 days. I also expect to receive registrable equity in BlackRock in the future."
Osborne was chancellor for six years before he lost his job following Britain's vote to leave the European Union in June last year.
The role , announced in January, will see Osborne provide advice on European politics, the Chinese economy and pensions.
"George has a unique and invaluable perspective on the issues that are shaping our world today," Larry Fink, chairman and chief executive of BlackRock, said at the time of the appointment.
Other senior British politicians have recently gone on to high-profile roles at financial firms.
Former prime ministers Gordon Brown and Tony Blair advise PIMCO and JP Morgan respectively while former U.K. foreign minister William Hague advises Citigroup.
CNBC contacted BlackRock for comment but at the time of publication had received no response.