You need your T4 slips to accurately report the amounts on your tax return. If you do not have them, you can call the Canada Revenue Agency at 1 800 959 8281 to get access to them.
As far as timelines go, employers are required to prepare and provide you with your T4 by the end of February, or, in the case of the 2019 taxation year (a Leap Year), because February 29 falls on a Saturday, you should be following up with your employer if they have not provided you with a T4 slip by the end of business March 2. In the case of former employers, you should expect a copy in the mail by the end of the first week of March.
In Canada, every employer is required by law to complete T4 statement of remuneration paid slips and summaries for the prior year by the last day of February, or, if the last day of February falls on a weekend, the first business day following that.
If an employer mails in the slips, the T4s must be postmarked on that day, or risk being assessed penalties.T4s for employment in 2019 are due Monday, March 2, 2020.
For the current taxation year (2019), the Turbotax software will be available by mid January, and some deadlines (i.e. RRSP contributions) fall later in 2020 (i.e. March 2), so, realistically, you should not be expecting to file your return until early or mid-March. If you owe money, you may postpone filing until the deadline of April 30, 2020.