On or before the last day of each month, each employer shall prepare and file a return for the preceding calendar month showing computation of the tax imposed by this article upon such forms as the finance director may prescribe, whether or not such taxes are due and owing to the City, and shall pay to the finance director all taxes deducted and withheld from the wages paid to its employees. If an employer fails to pay such tax, whether or not the employer deducts and withholds the same from the wages paid to its employees, such employer shall be responsible for the payment of the tax imposed by this article as though the tax had originally been levied against the employer. (Code 1979, § 36-156)