As of the last update in September 2021, there was no official requirement or provision to truncate the Social Insurance Number (SIN) on the employee copy of the T4 slip in Canada. The T4 slip is an important tax document that Canadian employers issue to their employees, reporting their employment income and deductions for the year.
As per CRA guidelines, we are required to mail out the T4s. We shouldn’t hand over or email the T4s. This guideline is to minimize the risks of breaching privacy.