The watchdog said yesterday that the bank's fixed income unit allowed traders to misrepresent the value of certain financial products over a period of five months.
These mispricings subsequently led to a write-down of $2.65 billion, which was announced by the bank earlier this year.
Margaret Cole, the FSA's director of enforcement, said: "It is imperative, particularly in more challenging financial conditions, that firms have in place appropriate systems and controls to manage their risks."
The bank's chief executive, Brady Dougan, admitted that the mispricings had been "unacceptable".
Credit Suisse has also been hit with a fine from the Securities and Exchange Commission, due to its activities on the New York Stock Exchange (NYSE).
The regulator has demanded a $350,000 penalty from the Zurich-based bank, after it made an administrative slip which allowed it to make trades ahead of clients' orders.
This is in direct contravention of NYSE rules.