Originally Posted by
themicah
Assuming you are flying to EWR from one of Canadian airports with US
CBP preclearance, then you will not have to recheck bags at EWR. If you are arriving at EWR directly from another Canadian airport (if UA even flies to any other Canadian airports...) then you will have to clear customs and recheck bags at EWR.
Note that if you are flying back through EWR to Canada from Tokyo, you WILL have to clear US customs and recheck bags at EWR on that trip.
For the person asking the question... you don't recheck your bags after clearing US customs in Newark. They will already be tagged by United for their final destination so all you have to do is hand them back over to United after carrying them through the exit of customs. There's a bag drop right there.