Irie Mon said "I filled my taxes on Sunday thinking I'd believe everything I was told about May 1st on a Sunday so taxed are due Monday May 2nd. Wrong. I filed on May 1st, got a immediate notice of Assessment and was charged interest for being one day late. Thank you Mr. Trudeau. My extra $13 will get you about .5 of a second of jet fuel while you fly around the world on our dollar. "
Are you sure that interest amount is for this filing? Their own website says you should be fine (someone else linked above), assuming everything is only for the 2021 tax year.
It's possible you had interest due for another reason. Can you get a statement of account or something online? The NOAs can be pretty opaque sometimes. I used to work at CRA and even I have a hard time making sense of them lol.
I would be curious if anyone else has this problem if it's genuinely wrong.