(b)referred to in section 392(2)(a), being an employer,does not deduct, or after so deducting fails to pay, or does not pay, the whole or any part of the tax, as required under this Act, and where the assessee has also failed to pay such tax directly, then, such person shall, apart from any other consequences that he may incur, be deemed to be an assessee in default within the meaning of section 398(1), in respect of such tax.