No, you will not have to claim your bags in SJU. If you are Canadian, you will have your bags checked right from SXM through to Toronto and go through customs there. You only have to go through customs at your first Canadian destination. We travel to Ottawa from SXM and have to claim our bags in Toronto, go through customs there and then recheck and travel on to Ottawa with no customs there when we get to our final destination. This is how it always was for us, unless something has recently changed.
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