As of January 2015, the balances on Subway cards can be checked by calling (877) 697-8222 as stated by MySubwaycard.com. Users can also look up their balances online or by going to certain Subway locations and requesting the assistance of a sales associate.
In order to access their balances, cardholders must know the PIN associated with their cards. There's a silver box on the reverse of Subway cards, which users can scratch off to reveal the PIN. When the balance on a card runs low, it's possible to reload it by using a credit card at a Subway location or online. One can also reload a card by paying in cash at a physical Subway restaurant. The maximum balance on a Subway card is $500.