If any taxpayer fails, neglects, or refuses to make and file his return as and when required under this chapter, the Director of Finance is authorized to determine the amount of tax payable, together with any penalty and/or interest assessed under the provisions of this chapter, and by mail to notify such taxpayer of the amount so determined, which amount shall thereupon become the tax and penalty and/or interest and shall become immediately due and payable. [Ord. 1703 § 11, 1975; Code 1970 § 9.28.110.]