S. 125.7(3) essentially feeds into s. 12(1)(x) by deeming “CEWS” wage subsidies to be government assistance received immediately before the end of the period (of approximately one month) in question. Notwithstanding that, CRA considers it to be quite possible that the assistance will be income under s. 9 rather than s. 12(1)(x). As for the timing of that income inclusion (under either s. 9 or 12(1)(x),) CRA indicated that the CEWS amounts must be included in the taxation year in which the periods fall even if the claims are not made (and received) until after the tax return has been filed for that taxation year. (This will require an amendment to the originally-filed return to be made.)
The one exception to this is illustrated by the example of a June 30, 2020 taxation year of the eligible entity, where the end of period 4 falls on July 4, 2020 (i.e., a few days after the taxation year end). In that case, if s. 12(1)(x) rather than s. 9 is considered to govern, there is a deemed receipt of government assistance on that date, so that the s. 12(1)(x) inclusion will fall into the subsequent taxation year.