Oyster is a way to pay for travel in London.
Oyster cards are smartcards that can be loaded with different types of tickets which can be read electronically by ticket gates and staff with ticket checking equipment. See here for further information and validity when using Oyster on National Rail services
Travelcard Season Tickets bought nominated Oyster retail outlets are loaded onto Oyster cards and their validity is exactly the same as a printed Travelcard ticket. If your Travelcard Season Ticket on Oyster does not cover the whole of your South West Trains journey, you must buy a paper ticket extension at the station where you start your journey, otherwise you may be liable to a penalty fare.
Nominated Oyster outlets also sells a ‘pay as you go’ service which can also be loaded onto an Oyster card and is valid for travel on Transport for London services. ‘Pay as you go’ cannot generally be used on National Rail services and cannot be used on South West Trains services. After making a 'pay as you go' journey you must 'touch out' and buy a valid ticket before boarding a South West Trains service, otherwise you may be liable to a penalty fare.
See here for latest Transport for London information on Oyster including touching in and out on National Rail services or contact TfL on on 020 7222 5600.
