In any case where a license tax is believed
by a licensee or applicant for a license to place an undue burden
upon interstate commerce or be violative of such constitutional clauses,
he or she may apply to the collector for an adjustment of the tax.
Such application may be made before, at, or within six months after
payment of the prescribed license tax. The applicant shall, by sworn
statement and supporting testimony, show this method of business and
the gross volume or estimated gross volume of business and such other
information as the collector may deem necessary in order to determine
the extent, if any, of such undue burden or violation. The collector
shall then conduct an investigation, and, after having first obtained
the written approval of the city attorney, shall fix as the license
tax for the applicant, an amount that is reasonable and nondiscriminatory,
or if the license tax has already been paid, shall order a refund
of the amount over and above the license tax so fixed. In fixing the
license tax to be charged, the collector shall have the power to base
the license tax upon the gross receipts, so long as the amount assessed
does not exceed the license tax as prescribed by this title. The collector
may require the applicant to submit, either at the time of termination
of applicant's business in the city, or at the end of each three-month
period, a statement by a certified public accountant as to the range
of the gross receipts and to pay the amount of license tax therefor,
provided that no additional license tax during any one calendar year
shall be required after the licensee shall have paid an amount equal
to the annual license tax.