§ 6. Payment and lien of tax. 1. To the extent the tax imposed by
section three of this part shall not have been previously paid pursuant
to section eight of this part,

(a) such tax, or the balance thereof, shall be payable to the
commissioner of finance in full at the time the report is required to be
filed, and

(b) such tax, or the balance thereof, imposed on any taxpayer which
ceases to do business in the city or to be subject to the tax imposed by
this part shall be payable to the commissioner of finance at the time
the report is required to be filed; all other taxes of any such
taxpayer, which pursuant to the foregoing provisions of this section
would otherwise be payable subsequent to the time such report is
required to be filed, shall nevertheless be payable at such time. If the
taxpayer, within the time prescribed by section five of this part, shall
have applied for an automatic extension of time to file its annual
report and shall have paid to the commissioner of finance on or before
the date such application is filed an amount properly estimated as
provided by said section, the only amount payable in addition to the tax
shall be interest at the rate set by the commissioner of finance
pursuant to section eighty-seven of part six, or, if no rate is set, at
the rate of six per centum per annum upon the amount by which the tax,
or the portion thereof payable on or before the date the report was
required to be filed, exceeds the amount so paid. For purposes of the
preceding sentence:

(1) an amount so paid shall be deemed properly estimated if it is
either (A) not less than ninety per centum of the tax as finally
determined (computed without regard to any credit allowable under
section four-a of this part), or (B) not less than the tax shown
(computed without regard to any credit allowable under section four-a of
this part) on the taxpayer's report for the preceding taxable year, if
such preceding year was a taxable year of twelve months; and

(2) the time when a report is required to be filed shall be determined
without regard to any extension of time for filing such report.

2. The director of finance may grant a reasonable extension of time
for payment of any tax imposed by this part under such conditions as it
deems just and proper.

3. Subdivision one of this section shall apply to a taxpayer which has
a right to a credit pursuant to section four-a of this part, except that
the tax, or balance thereof, payable to the director of finance in full
pursuant to subdivision one of this section, at the time the report is
required to be filed, shall be calculated and paid at such time as if
the credit provided for in section four-a of this part were not allowed.