You can look at your CRA Notice of Assessment as a receipt for filing your tax return and an annual statement that tells you how much income tax you owe, how much you can expect for a tax refund, what income tax you already paid and any tax credits that you are eligible for.
The NOA is calculated from the information that you submit on your tax return and contains a lot of information that you may need to make future financial decisions. If you have a RRSP then the NOA is particularly helpful as it tells you the maximum contribution that you can make to your RRSP in the following year. It is important to know how much room you have so that you do not over contribute and have to pay penalties. If you participated in the Home Buyer's Plan or the Lifelong Learning Plan and withdrew from your RRSP for those purposes then your NOA will tell you when future payments are due and how much you need to pay.
You should always keep your notice of assessment in a file along with your receipts for that tax year. If you see anything in your Notice of Assessment that does not seem correct to you, you have 90 days to formally object or make amendments to any of the information on the document. A NOA will also inform you if you happen to be the subject of an audit from the CRA. If you do not agree with the reasons for an audit you have 90 days to make a formal objection.
You can get your NOA in two ways, in the mail from the CRA or when the CRA notifies you that your assessment is available for you to view via CRA Online Mail. You can register for CRA Online Mail through your CRA MyAccount. If you lose your paper copy you can use MyAccount to view and print your notices of assessment or reassessment, this includes any notices issued since Feb 9th 2015, and summaries of notices issued after 2004. If you filed your taxes using NETFILE it can take up two weeks to see your Notice of Assessment.
From an article by Wealth Simple
Will Covid-19 Relief Measures Affect my Taxes?
Is it Time for the Annual Clean-up and Back-up of your Files?
When can you Expect your Tax Refund this year?
Are you one of the Almost 50% of Canadians Taking Advantage of the Tax Deadline Extension?
How to Minimize Taxes on Your Small Business
What you Need to Know About Filing Coupled Tax Returns
Ever Wondered how the Government Spends Your Tax Dollars?
The CRA has $1billion in Uncashed Cheques