Yes true. The assessing officer is a quasi judicial authority and he must follow the rules of natural justice while making assessment or taking any action against the dealer or assessee.
It is seen that sometimes the authority in an act is provided with a discretionary power to decide on a particular matter but in that case too that discreationary power should be exercised judicialy, reasonably and not arbitrarily. Rules of natural justice (like opportunity of being heard) must be followed while taking every administrative action.