China's biggest brokerage overstated its derivatives business by $166 billion

As errors go, it's a big one.

Citic Securities, the biggest financial brokerage in China, overstated its derivative business by $166bn (£110bn) from April to September, according to a BBC report that cites figures from the Securities Association of China.

Citic blamed the error on a "system upgrade" and said it has been corrected.

The error occurred in data for Citic's equity swaps business, which is closer to $6.2 billion in size, according to the report.

Investors shrugged off the news, and Citic shares fell less than 1%.

Equity swaps are derivatives contracts where two firms agree to swap income from shares and fixed interest rates.

It's not the first time Citic has been under scrutiny. The company has been the focus of a regulatory crackdown in the wake of China's market crash in August.

The FT reported last week that Citic's chairman was forced out of the company because of an insider-trading scandal involving senior executives.