I had this same error, called the CRA, no help, called UFile, no help.
Now I looked better at the error.
Step 5: Netfile.
Clicked on the Federal link there.
Now it shows me the error code and gives me an option to file again.
However, between these 2 sections there is a sneaky little line.
Something like, if you have a middle name you need to provide that as CRA needs it for first time filers
So I filled that in, tried to submit again and it worked!
Getting error 31 when filing tax for 1st time, I verified all the SIN info
in NETFILE and filing
Posted
I had this same error, called the CRA, no help, called UFile, no help.
Now I looked better at the error.
However, between these 2 sections there is a sneaky little line.
Something like, if you have a middle name you need to provide that as CRA needs it for first time filers
So I filled that in, tried to submit again and it worked!
Hope this helps someone