"If you Netfiled, and you got an error about your OAS amount in TurboTax being incorrect, then in your situation, I would go into Forms mode and go inspect my T4(OAS) slip and line 11300 on my T1 form. I would also log into MyAccount on the CRA website and download a copy of the T4(OAS) slip submitted to the CRA by Services Canada, in order to compare both sides."
There's the rub.
Unless the filer has chosen the auto-fill option and then tried to change the input, there is no way for the program to even know that the amount is wrong.
And there is no use in comparing what was mailed to what is on CRA's site as, once again the program has no way to compare and determine an error.
It is another documented bug.
