The NOA is not a requirement as long as you have the employer letter.
From Documents check list:
You must provide proof of qualifying work experience, including:
• a copy of your most recent authorization to work in Canada (i.e. work permit or visitor record)
• employer reference letters for all periods of qualifying work experience you identify in your application
• copies of your T4 tax information slips and your Notice of Assessment (NOA) issued by the Canada Revenue
Agency for the period(s) of work experience you identify in your application (CIC preferred),
OR
• a sufficient combination of other supporting documentation, which could include copies of a record or letter of employment from the employer in Canada, work contracts and pay stubs for the period(s) of work experience you identify in your application.
So it is not mandatory as long as you show enough proof of your employment.
In my case, I sent a copy of my T4 (which was only showing 4 months), contract and a letter of my employment.
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