P.R. Laws tit. 13, § 30171
(a) Computation of taxable income. — Taxable income shall be computed on the basis of the taxpayer’s taxable year.
(b) Taxable year. — For purposes of this part, the term “taxable year” means:
(1) The taxpayer’s annual accounting period, if it is a calendar year or a fiscal year;
(2) the calendar year, if subsection (g) applies, or
(3) the period for which the tax return is filed, if a tax return is filed for a period of less than twelve (12) months.
(c) Annual accounting period. — For purposes of this part, the term “annual accounting period” means the annual period on the basis of which the taxpayer regularly computes his/her income in keeping his/her books.
(d) Calendar year. — For purposes of this part, the term “calendar year” means a period of twelve (12) months ending on December 31.
(e) Fiscal year. — For purposes of this part, the term “fiscal year” means a period of twelve (12) months ending on the last day of any month other than December.
(f) Taxable year consisting of fifty-two (52) and fifty-three (53) weeks. —
(1) Election of year consisting of fifty-two (52) and fifty-three (53) weeks. — A taxpayer who, in keeping his/her books, regularly computes his/her income on the basis of an annual period which varies from fifty-two (52) to fifty-three (53) weeks and ends always on the same day of the week and ends always:
(A) On whatever date such same day of the week last occurs in a calendar month, or
(B) on whatever date such same day of the week falls which is nearest to the last day of a calendar month, may (in accordance with the regulations prescribed by the Secretary) elect to compute his/her taxable income for purposes of this part on the basis of such annual period.
(2) Special rules for fifty-two (52) to fifty-three (53) weeks taxable year. —
(A) Effective dates. — In any case in which the effective date or the applicability of any provision of this part is expressed in terms of taxable years beginning, including, or ending with reference to a specified date which is the first or last day of a month, a taxable year described in clause (1) shall be treated:
(i) As beginning with the first day of the calendar month beginning nearest to the first day of such taxable year, or
(ii) as ending with the last day of the calendar month ending nearest to the last day of such taxable year, as the case may be.
(B) Change in the annual accounting period. — In the case of a change from or to a taxable year described in clause (1) of this subsection:
(i) If such change results in a short period of three hundred fifty-nine (359) days or more, or of less than seven (7) days, § 30264(c) of this title (relating to alternative tax computation) shall not apply;
(ii) if such change results in a short period of less than seven (7) days, such short period shall, for purposes of this section, be added to and deemed a part of the following taxable year, and
(iii) if such change results in a short period to which § 30264(c) of this title applies, the taxable income for such short period shall be placed on an annual basis for purposes of such subsection by multiplying such income by three hundred and sixty-five (365) and dividing the result by the number of days in the short period, and the tax shall be the same part of the tax computed on the annual basis as the number of days in the short period is of three hundred and sixty-five (365) days.
(g) No books kept; no accounting period. — Except as provided in § 30264 of this title (relating to tax returns for periods of less than twelve (12) months), the taxpayer’s taxable year shall be the calendar year if:
(1) The taxpayer keeps no books;
(2) the taxpayer does not have an annual accounting period, or
(3) the taxpayer has an annual accounting period, but such period does not qualify as a fiscal year.
History —Jan. 31, 2011, No. 1, § 1040.01, retroactive to Jan. 1, 2011.