It seems the underlining issue is when info put in conflicts with what CRA has one file. So George's example falls under that, and mine too.
In my case, self-employment commissions which was auto-pulled from CRA for a T4A is required to also go on the T2125 as Income. But I also filled the line for 'GST Included in Sales' (Something I've always done with the 'Gross Sales/Income' line), but I suppose it is not compatible when being applied to info from a T4A.
The UFile Support agent pointed out the issue in a a quick minute, without having to see my Return. So I'm not sure why they can include such tips in the software.
(and if you are like me, weary of calling support... don't worry, there was only a brief wait, and the rep was fairly straight to the point and knowledgeable enough)
