CRA confirms that a graduated rate estate can have up to four taxation years

If the executors of an estate adopt a year end that results in an initial short taxation year (say, September 30, 2016, being six months after the death), then the estate generally would be deemed by s. 249(4.1) to have a further short taxation year, namely, its 4^th taxation commencing on November 1, 2018 and ending on March 31, 2019, being 36 months after the death. Thereafter, the estate would not enjoy graduated rates and would be required to use a December 31 year end.

Neal Armstrong. Summary of 19 June 2015 STEP Roundtable, Q. 1, 2015-0572131C6 under s. 249(4.1).