You need to stay in Canada 48hrs to take home $800 in merchandise. Under 48 hours you are allowed $200. If you have over that amount you will pay duty. They will take debit, credit or cash to pay the duty. I think your duty rate is 3%
You may take groceries back no citris but veggies grown in Canada are ok as well as canadian meat
You may combine your amount together within a family at the same address.
I hope this is up to date, our friends live in Virginia and this is what I recall. You could go online and check with your customs officer.
