Welcome to the Community! With tax season just around the corner, it's essential to get T4s prepared for you employees. I can shed some light on the process for you.
You can find detailed instructions on how to prepare and submit your T4 slips and summary in the following Community article: How to prepare T4 slips and summary. As for why the to do list isn't appearing in the payroll overview screen, this could be a performance issue caused by a build up of cache and other site data within your browser. I recommend trying the following troubleshooting steps, checking between each to see if the to do list reappears: