The recent 2017 Canadian Payroll Year End Update has an error/bug in the T4 Electronic XML file format.
There are no separate steps to close A.A. as the year-end close process is automatically integrated with the year-end close process for General Ledger.
The year-end close process moves all your current data into the last year tables. There is no consideration for date. You must complete all 2020 payrolls and run the file reset process before processing any 2021 pay runs.