What would happen if I leave my Invisalign out for a day and put them back in at night?

Yes, it will adversely affect your treatment and final results. Your case will get off track and lead to unnecessary refinements which will only add more time and effort to obtain the results you and your dentist want. If the refinement is due to your non-compliance your dentist may even bill you for the additional work caused by not following the prescribed regimen.If you are unable to wear your aligners for 20-22 hour per day, you will need to add additional days to your treatment. For instance: If you are only wearing them for 12 hours per day, you will need to add that time back. So, for every two days of wearing only twelve hours, you need to add on two additional days of wearing at 12 hours or one full day of 20-22 hour wear. It is basically going to take you twice as long to get the final results which were planned and designed by your dentist.