Thank you for your question.
If you are making mistakes as you are completing your income tax return you are going to be reassessed and will need to pay back what the government gives you ( if you are entitled to it) and this can also cause penalties in being late filing your tax return if you are needing to pay. Complete your tax return step by step being truthful and answering the questions as they are asked. If you need assistance please reach out to our support team. (put the link)
As per CRA: The Canada Revenue Agency will only accept one return per tax year. Once you've filed your return (mistakes and all), you can't file a new one. But you can correct the original by way of an adjustment to your return.
Here is a Turbotax guide on how to amend your tax return.
Here is an FAQ on how to amend your tax return.
If you have any questions, you can contact our phone support team or contact us via private chat on Facebook or Twitter.