§ 75. Interest on underpayment. 1. General.--If any amount of tax is
not paid on or before the last date prescribed in whichever of the named
parts is applicable for payment, interest on such amount at the rate set
by the commissioner of finance pursuant to section eighty-seven, or, if
no rate is set, 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.

2. Exception as to estimated tax.--This section shall not apply to any
failure to pay estimated tax under part two or part three of this title.

3. 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 whichever of the named
parts is applicable (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.

5. 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 director of finance 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.

6. Tax reduced by carryback.--If the amount of tax under part two 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 filing date for the
taxable year in which the net operating loss arises. Such filing date
shall be determined without regard to extensions of time to file.

7. 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 the taxes under the named parts. Any reference in this
part to the tax imposed by the named parts, or any of them, shall be
deemed also to refer to interest imposed by this section on such tax.

8. Interest on penalties or additions to tax.--Interest shall be
imposed under subdivision one 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 two of section eighty-three 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.

9. Payment prior to notice of deficiency.--If, prior to the mailing to
the taxpayer of a notice of deficiency under subdivision two of section
seventy-two, the director of finance 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 director of finance, 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.

10. Payment within ninety days after notice of deficiency.--If a
notice of deficiency under section seventy-two 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.

11. Payment within ten days after notice and demand.--If notice and
demand is made for payment of any amount under subdivision two of
section eighty-three, 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.

12. 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.

13. Interest on erroneous refund.--Any portion of tax or other amount
which has been erroneously refunded, and which is recoverable by the
commissioner of finance, shall bear interest at the rate set by the
commissioner of finance pursuant to section eighty-seven, or, if no rate
is set, at the rate of six percentum 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.

14. 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.