HSBC's Swiss-based private banking arm, HSBC Private Bank, amassed as many as 368 US clients and collected fees of about $5.7 million for conducting securities transactions and other cross-border brokerage services in the US, the SEC said.
However, the HSBC Swiss relationship managers were not registered investment advisers or broker-dealers, as is required under US law, the agency said.
"HSBC's Swiss private banking unit illegally conducted advisory or brokerage business with US customers," said Andrew Ceresney, director of the SEC's enforcement division.
The unit's "efforts to prevent registration violations ultimately failed because their compliance initiatives were not effectively implemented or monitored."
The Geneva-based subsidiary decided to exit the cross-border brokerage business with US clients in 2010.
In settling the case, HSBC Private Bank agreed to admit the facts in the SEC order and acknowledge that it had violated federal securities laws, the agency said.
The SEC fine follows a disclosure Friday by the HSBC unit that it had been placed under formal investigation as part of a French tax fraud probe.
In France, being placed under formal investigation is the nearest equivalent to being charged, and occurs when an examining magistrate decides there is a case to be answered.
The French newspaper Le Monde reported that French investigators had calculated that the bank had assisted more than 100,000 people and 20,000 companies hide some 180 billion euros ($225 billion) in 2006 and 2007.
The same Swiss subsidiary was charged on November 17 in Brussels with fraud and money-laundering worth hundreds of millions of euros, mainly for helping diamond dealers in the industry's international hub of Antwerp evade Belgian taxes.