Retro Pay for Wage Mistake

My question involves employment and labor law for the state of: California
I recently found out that my place of employment has been paying me probationary wages for approximately 2 years (after probationary time), when I was suppost to be at the mid level pay scale. In confronting the management, the statement was made that "we just don't have the money to pay you." Are they required to retro back because they made a mistake. When I got off probation they said that I was going to be promoted to the next pay scale yet they didn't. Others had the same problem and received retro pay, but since mine went so long before I found it they won't retro me back. Thankyou for your time.

The law only requires that you be paid the higher of state or Federal minimum wage. The law does not EVER require that you be granted a wage increase, let alone a retroactive one, unless minimum wage is raised by the appropriate legislative body and you are earning less than the new minimum.

So no, they are not required to provide retro back pay, even if they made a mistake, unless you are earning less that the state (which is the higher of the two) minimum wage. They are not even required to increase your pay going forward, with the same caveat.