When do I clear customs?
 

New to international travel. I am not sure what I'll need to do . My trip is scheduled for late August. For my return to the US, I'll be flying Halifax to Toronto to Columbus. Will I clear customs in Toronto? Wondering what I have to do with my checked luggage. Will I be able to check my bags back to Columbus or will I have to get my bag in Toronto and recheck it? Thanks for your help.

You will clear immigration and customs in Toronto. I haven't connected in Toronto recently, so I can't speak to your luggage questions.

Toronto is one of the airports that USA officials do immigration & customs pre clearance. So land in USA like a domestic flight.
As normal for USA immigration & customs, crossing the USA border, would expect all carry on and checked bags will be checked.

https://www.cbp.gov/travel/preclearance
https://en.wikipedia.org/wiki/United...r_preclearance

Take a look at this thread:

Thanks for all the resources.