Credits and deductions

Report in 2018 Tax return:

RRSP contribution March 2, 2018, - Dec 31, 2018 > remainder of the year

RRSP contribution Jan 1, 2019, - March 1, 2019 > first 60 days

unused contribution from prior years in any > found in the notice of assessment or AFR (has to be reported before)

Report in 2019:

RRSP contribution March 2, 2019, - Dec 31, 2019 > remainder of the year

RRSP contribution Jan 1, 2020, - March 1, 2020 > first 60 days

unused contribution from prior years in any > found in the notice of assessment or AFR (has to be reported before)

If there is any contribution in 2018 that has not been reported yet, and you have already filed your 2018 tax return > you will need to file a T1-Adjustment for 2018 or Refile the 2018 return to include the new information. 

Below is an example screenshot from TurboTax online:

I hope this was helpful