T4 BOX 45 Amendment to code 1 for just group for employees out of thousands of employees in entity

Hi There,

Hope you are good!

Regarding T4 Box 45, we have defaulted the system to code 3 . However, now we have group of employees (specifically 82 employees) for whom the T4 Box 45 must reflect code 1. The T4 file have already been submitted to CRA and we are looking for a way to amend code to 1 for those 82 employees.

Please advise how to amend the code for just a group of employees out of whole legal entity.

Is it we have to do it manually on CRA website or we need to create an informational element. If its creation of information element then please provide steps.