For a SC 186 the employer must offer you a minimum of 2 years of employment at the nomination stage. However (unlike the SC187 visa) once the SC186 visa is granted – there is no condition requiring the visa holder to remain with that employer and there are no grounds for a visa cancellation by the Department – should you, as the visa holder leave your employment with that employer.
It is for these very reasons that many Australian employers have become disenchanted with offshore workers as they don’t believe their loyalty and assistance has been properly “reciprocated”.
Also, there is no specific requirement to inform DIBP as to that change in circumstance (which would usually be required via a Form xxxx).
Obviously, the terms of the employment contract signed by the SC186 visa holder and the employer need to be adhered to, and there are also moral issues for the visa holder to consider if he/she is considering resigning from an employer before the end of the two year period, considering the employer has acted in good faith, supported you in making an application for permanent residence and taken a risk.