If you are referring to a 2018 slip:
If you have signed up for the CRA’s My Account
service and the T4 is there, you can use Auto-Fill to get that slip. If you
used Auto-Fill previously, you can run it again to get the new slip.
If you can’t use Auto-Fill or it doesn’t have the
T4 you are looking for, you’ll need to contact the company you work for to get
one.
If you are referring to a 2019 slip:
Companies are not required to issue T4 slips until
the begging of the next year. You’ll likely get one in early 2020.