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If she writes a notarized letter explaining that we live with them and that all utility accounts are in her name then maybe include Where it shows us on her insurance registered to our address ? Also for government issued documents can I use my old study permit from the end of 2017 as proof too? I just don’t know if they will send the application back because it’s not accepted proof. Have you ever seen other people do it on the forum?

Yes, you can use those. IRCC documentation is good.
 
No. We had lots of other proofs.
I see. I have noticed that every single case is very different and unique. Some are more simple than others but hopefully all will work out. Did you use a lawyer?
 
I see. I have noticed that every single case is very different and unique. Some are more simple than others but hopefully all will work out. Did you use a lawyer?

No. A lawyer is not needed. Majority do it themselves.