RRSP contribition $40,000.00 & Total income $90,000.00 (Mostly T4 & nominal investment income)
Total income $150,000.00 (Pension cash lump sum, bonus, CPP, OAS)
$40,000.00 RRSP deduction should be utilized in 2019 because income will be much higher.
Considerations were impacts on Age amount, Ontario surtax, Ontario health premium, & Marginal tax bracket.
However, even without considering these it seems the obvious choice to use the deduction is in 2019 if the number one priority is lowering overall tax paid between the two years.
Even with the full deduction being applied in 2019 income is $110,000, which is still higher than the $90,000.
Possible rate of return on investments earned from 2018 to 2019 omitted in this scenario.