The Canada Revenue Agency (CRA) permits you to file amended T4 slips electronically and on paper.
If you want to submit original slips that were not filed with your original return, follow the steps for filing original T4 slips (by paper or electronically) and submit them as a separate return. Do not include original slips with an amended T4 slip return.
Before distributing amended slips to employees, remember to write the word amended on each slip before handing them out.