Installment sales.

(i) A prior election by a taxpayer to report a gain from an earlier year sale on the installment basis for Federal income tax purposes, but not for New York State personal income tax purposes under former article 16 of the Tax Law, will give rise to a modification under this subdivision. The modification will be the amount of such installment gain included in the taxpayer's Federal adjusted gross income for the taxable year which was previously properly included (because of such taxpayer's election) in a New York State personal income tax return filed by such taxpayer under former article 16 of the Tax Law.

(ii) Where a sale was made during 1958 (when the normal New York State personal income tax was cancelled) and the taxpayer elected to report it on the installment basis for Federal income tax purposes, such taxpayer will be deemed to have made the same election for New York State personal income tax purposes, in the absence of proof to the contrary, so that the modification referred to in this subdivision is not allowable. However, if the taxpayer elected to report the full amount of a 1958 gain for the purposes of an applicable New York State personal income tax which was not cancelled (capital gains tax or unincorporated business tax), but reported it on the installment basis for Federal income tax purposes, a modification will be allowed. That is, such a taxpayer may subtract from Federal adjusted gross income for any subsequent year whatever may have been included therein as an installment of the gain from the 1958 sale.