The form cannot be submitted until you are within 48 hours of your entry date. Before the 48-hour timeframe, you can advance the process by registering on the site and completing the questions; however, you must wait until you’re within the 48-hour timeframe to submit. (This is to avoid excess records in the immigration system).
It is best to complete the form on a desktop or laptop rather than a mobile device.
You will receive a response via email, and you will need to print it out and carry it with you.
To make things speedier during check-in at the immigration desk, highlight your name, pre-check #, and date of travel.