Section 5. Accounting periods and methods

--(a)  Accounting  periods.--A
  taxpayer's taxable year under this local law shall be the  same  as  his
  taxable year for federal income tax purposes.
    (b)  Change  of  accounting  periods.--If a taxpayer's taxable year is
  changed for federal income tax purposes, his taxable year  for  purposes
  of  this local law shall be similarly changed. If a taxable year of less
  than twelve months results from a  change  of  taxable  year,  the  city
  standard  deduction,  and the city personal exemptions shall be prorated
  under regulations of the administrator.
    (c) Accounting methods.--A taxpayer's method of accounting under  this
  local  law  shall  be  the  same as his method of accounting for federal
  income tax purposes. In the absence of  any  method  of  accounting  for
  federal income tax purposes, city taxable income shall be computed under
  such  method  as  in  the  opinion of the administrator clearly reflects
  income.
    (d) Change of accounting  methods.--(1)  If  a  taxpayer's  method  of
  accounting  is  changed  for  federal income tax purposes, his method of
  accounting for purposes of this local law shall be similarly changed.
    (2) If a taxpayer's method of accounting is changed, other  than  from
  an  accrual  to  an installment method, any additional tax which results
  from adjustments determined to be necessary  solely  by  reason  of  the
  change  shall  not  be  greater  than  if  such adjustments were ratably
  allocated and included for the  taxable  year  of  the  change  and  the
  preceding  taxable  years,  beginning after July first, nineteen hundred
  sixty-six, not in excess of two, during  which  the  taxpayer  used  the
  method of accounting from which the change is made.
    (3) If a taxpayer's method of accounting is changed from an accrual to
  an installment method, any additional tax for the year of such change of
  method  and for any subsequent year which is attributable to the receipt
  of installment payments properly accrued  in  a  prior  year,  shall  be
  reduced by the portion of tax for any prior taxable year attributable to
  the accrual of such installment payments, in accordance with regulations
  of the administrator.