(a) In the case of an estate, trust or partnership which was not in existence for the entire 12 months of its normal taxable year, the short period which the taxpayer was in existence during such 12 months is a taxable year for which a New York State income tax return must be filed. Examples of such short taxable years are as follows:

1. (1) If a partnership is terminated and completely liquidated during its normal taxable year and this results in an accounting period of less than 12 months for Federal income tax purposes, such period is a taxable year for which a New York State partnership return must be filed.
2. (2) The first New York State fiduciary return of an estate or trust will often be a short- period income tax return, due to the choice of an accounting period by the fiduciary which is either a calendar year or fiscal year. For an estate, the first New York State fiduciary return would cover the period from the day following the decedent's death to the start of the regular tax year selected by the fiduciary; for a trust, the first New York State fiduciary return would cover the period from the date the trust was established to the beginning of the trust's regular tax year, as selected by the trustee.
3. (3) The final New York State fiduciary return of an estate or trust will in many situations be a short-period income tax return, due to the termination of administration with respect to the estate, or the termination of the trust, during its normal taxable year.