GO Transit commuters will be able to get their money back starting Thursday if their train is more than 15 minutes late.
But it won't apply when delays are caused by extreme weather, police investigations, accidents or medical emergencies.
For other delays, such as those caused by mechanical troubles, riders can get a refund.
People who use the electronic Presto card can submit their claims online using a form on GO Transit's website.
Customers using tickets or other passes can ask for a credit at GO stations.
GO Transit, a division of the provincial agency Metrolinx, said it runs more than 180 train trips and over 2,100 bus trips carrying about 217,000 passengers on a typical weekday.