Legal Question in Business Law in California

There is no cause of action called simply "unfair business practices." So there is no specific limitations period. Unfair insurance practices are based on the insurance policy, which is a contract in writing, meaning a four year limitations period applies. Without knowing the actual cause of action that you are calling "unfair business practices" there is no way to say which statute of limitations would apply.

One statute of limitations that may apply to a large number of cases involving "unfair business practices" is found in Business & Professions Code section 17208, and it's four years. However, applying the proper statute and applying it to the facts of a particular case is not always straightforward. There are questions of when the limitations period begins to run, and whether anything has happened to "toll" (suspend) its running as well as whether the statute your're attempting to apply is the right one under the facts and circumstances. However, four years would be a good starting point for a case under B&P sections 17000 et. seq,, the Unfair Practices Act, one of our most basic laws against unfair business practices, and probably for suits based on other similar California laws.