§ 64. Interest on underpayment.--(a) General.--If any amount of income
tax is not paid on or before the last date prescribed in this local law
for payment, interest on such amount at the rate of six percentum per
annum shall be paid for the period from such last date to the date paid,
whether or not any extension of time for payment was granted. Interest
under this subdivision shall not be paid if the amount thereof is less
than one dollar. If the time for filing a return of tax withheld by an
employer is extended, the employer shall pay interest for the period for
which the extension is granted and may not charge such interest to the
employee.

(b) Exception as to estimated tax.--This section shall not apply to
any failure to pay estimated tax under section thirty-six.

(c) Exception for mathematical error.--No interest shall be imposed on
any underpayment of tax due solely to mathematical error if the taxpayer
files a return within the time prescribed in this local law (including
any extension of time) and pays the amount of underpayment within three
months after the due date of such return, as it may be extended.

(d) No interest on interest.--No interest under this local law shall
be imposed on any interest provided by this title.

(e) Suspension of interest on deficiencies.--If a waiver of
restrictions on assessment of a deficiency has been filed by the
taxpayer, and if notice and demand by the administrator for payment of
such deficiency is not made within thirty days after the filing of such
waiver, interest shall not be imposed on such deficiency for the period
beginning immediately after such thirtieth day and ending with the date
of notice and demand.

(f) Tax reduced by carryback.--If the amount of tax for any taxable
year is reduced by reason of a carryback of a net operating loss, such
reduction in tax shall not affect the computation of interest under this
section for the period ending with the last day of the taxable year in
which the net operating loss arises.

(g) Interest treated as tax.--Interest under this section shall be
paid upon notice and demand and shall be assessed, collected and paid in
the same manner as income tax. Any reference in this title to the tax
imposed by this local law shall be deemed also to refer to interest
imposed by this section on such tax.

(h) Interest on penalties or additions to tax.--Interest shall be
imposed under subdivision (a) in respect of any assessable penalty or
addition to tax only if such assessable penalty or addition to tax is
not paid within ten days from the date of the notice and demand therefor
under subdivision (b) of section seventy-two, and in such case interest
shall be imposed only for the period from such date of the notice and
demand to the date of payment.

(i) Payment prior to notice of deficiency.--If, prior to the mailing
to the taxpayer of a notice of deficiency under subdivision (b) of
section sixty-one, the administrator mails to the taxpayer a notice of
proposed increase of tax and within thirty days after the date of the
notice of proposed increase the taxpayer pays all amounts shown on the
notice to be due to the administrator, no interest under this section on
the amount so paid shall be imposed for the period after the date of
such notice of proposed increase.

(j) Payment within ninety days after notice of deficiency.--If a
notice of deficiency under section sixty-one is mailed to the taxpayer,
and the total amount specified in such notice is paid on or before the
ninetieth day after the date of mailing, interest under this section
shall not be imposed for the period after the date of the notice.

(k) Payment within ten days after notice and demand.--If notice and
demand is made for payment of any amount under subdivision (b) of
section seventy-two, and if such amount is paid within ten days after
the date of such notice and demand, interest under this section on the
amount so paid shall not be imposed for the period after the date of
such notice and demand.

(l) Limitation on assessment and collection.--Interest prescribed
under this section may be assessed and collected at any time during the
period within which the tax or other amount to which such interest
relates may be assessed and collected, respectively.

(m) Interest on erroneous refund.--Any portion of tax or other amount
which has been erroneously refunded, and which is recoverable by the
administrator, shall bear interest at the rate of six per centum per
annum from the date of the payment of the refund, but only if it appears
that any part of the refund was induced by fraud or a misrepresentation
of a material fact.

(n) Satisfaction by credits.--If any portion of a tax is satisfied by
credit of an overpayment, then no interest shall be imposed under this
section on the portion of the tax so satisfied for any period during
which, if the credit had not been made, interest would have been
allowable with respect to such overpayment.