Yes, propane tanks do expire! Pa. state law requires all propane tanks to be recertified after 10 years. The expiration date is stamped into the metal collar around the valve at the top of the tank. Expiration occurs at the end of the month that is stamped on the tank. This particular tank expires after the last day of May, 2019. At that point this would either need to be recertified or disposed of and a new tank purchased. When a tank has been recertified it will have another date stamped or engraved into the same general area and will then be good for another 5 years after the last day of the month of recertification. (Fishers Ace does not do recertification of propane tanks.)