I need to change my marital status from Common Law to Single

[pjalisappi]

I became single October 2015 and already filed for that year, and so 2016 I filed single.

[TonyC11]

You cannot change back to Single status for CRA tax purposes!

Once you file as Common-law, your Marital status can only be changed to Married, Separated or Widowed.

( and if you filed as Married, you can change to Separated, Divorced or Widowed).

In CRA terms you can never go back.