basically trying to find how to avoid paying tax on the portion already contributed as RRSP.
RRSPs purchased before Feb 28, 2017 are required to have been reported on the 2016 tax return. If you did not do this, then you will have to adjust the 2016 return to include the RRSP contribution. You are able to decide not to use the deduction on the 2016 return, and it would be available then to be used as an unused RRSP contribution on the 2017 tax return.
To file an adjustment for your 2016 tax return:
https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/change...
RRSPs purchased before Feb 28, 2017 are required to have been reported on the 2016 tax return. If you did not do this, then you will have to adjust the 2016 return to include the RRSP contribution. You are able to decide not to use the deduction on the 2016 return, and it would be available then to be used as an unused RRSP contribution on the 2017 tax return.
To file an adjustment for your 2016 tax return:
https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/change...
Unfortunately this doesn't give the answer I was looking. I understand that RRSP from March 2017 to Feb 2018 will be used in 2017 taxes but the question is that if a retiring allowance was received in January 2017 and a certain % of that amount was deposited directly in RRSP in Feb 2017 ( before March deadline and thus contributing in 2016 taxes), how should we offset that amount ( getting net income after subtracting RRSP from retiring allowance of T4). CRA suggested using Line 230 Schedule 7 but where to get that in Turbo Tax and what to Fill?