Welcome to the Community. I'd be happy to help with showing you how to access your T4s from 2018.
Your past payroll forms are accessible once archived. Here's how to view an archived payroll form:
From the left menu, select Taxes, then Payroll Tax.
Under Monthly Forms or Annual Forms, select View Archived Forms.
Select the desired form.
Select View.
The available liability periods only extend back for a year or two. If you need to archive a form from an earlier period, I'd suggest reaching out to our Payroll Specialists for assistance. You can open a chat conversation with our experts through this link: https://help.quickbooks.intuit.com/en_CA/contact.