Well, it is likely too late for the 2020 taxation year. Typical methods of reducing your income taxes include making sure you have not lost any receipts for the expenses you could claim on your personal tax return. These items include medical expenses and charitable donations.
Are you entitled to credits you are not claiming? For example, is it possible that you or a member of your family could qualify for the disability tax credit? Could a student in your family be transferring tuition to you? Do you have a dependent child and not a spouse? There may be a tax credit available.
The main ways people can lower their taxes without spending money on RRSP’s is to claim all the credit they are entitled to and find all their receipts.