State those circumstances, under which a "postal ballot form" can be considered invalid according to the provisions of Secretarial Standard-II.

As per para of 16.5.3 of Secretarial Standard-II, a postal ballot form shall be considered invalid if: A form other than one issued by the company has been used; It has not been signed by or on behalf of the member; Signature on the postal ballot form doesn't match the specimen signature with the company; It is not possible to determine without any doubt the assent or dissent of the member; Neither assent nor dissent is mentioned; Any competent authority has given directions in writing to the company to freeze the voting rights of the member; The envelope containing the postal ballot form is received after the last date prescribed; The postal ballot form, signed in a representative capacity, is not accompanied by a certified copy of the relevant specified authority; It is received from a member who is in arrears of payment of calls; It is defaced or mutilated in such a way that its identity as genuine form cannot be established; Member has made any amendment to the Resolution or imposed any condition while exercising his vote.