Is it possible to change an amount on last years tax form and re-submit to canada revenue agency?

Yes, you can still make changes after you have filed your tax return. You can use ReFile in TurboTax or you can use the Canada Revenue Agency (CRA)’s My Account service to make the changes. But you may want to wait until you have gotten your Notice of Assessment, as the CRA may correct the error themselves. This TurboTax FAQ has more information on changing a filed return: I've filed my tax return. Can I still make changes?