Canada Revenue Agency (CRA) offers an excellent service for helping you prepare your individual income tax return. You need to register for My Accountwith CRA (which you should do anyway) and you need to be using tax software. CRA does not have the ability to download data to a tax return prepared on paper (accounting humour).
Your software will have an option to Auto-fill and when you select that option the CRA website will fill in the information from your T4, T5, T3, OAS, CPP, T4E, T4RIF, T4RSP, etc. It will also pick up any RRSP contributions that you have made.
Auto-filling your return will save you time and also mean that you don’t miss any slips, so your return will be more accurate. If you use this service you won’t be getting any letters from CRA saying that they had to adjust your return which is yet another benefit of using Auto-fill.