Assessment not voidable

No assessment or other proceedings purporting to be made, issued or executed under this Act, shall be,ó

1. (a) quashed or deemed to be void or voidable for want of form; or
2. (b) affected by reason of mistake, defect or omission therein, if it is in substance and effect, in conformity with this Act or the rules made thereunder and the person assessed, or intended to be assessed or affected by the document is designated in it according to common understanding.