If you are a Travelcard (or Freedom Pass) holder, you are allowed to use a combination of it and an extension ticket to make a through journey across the zonal boundary, and the train is not required to call at the boundary station.

This article shows a demonstration to buy an extension ticket, called boundary fare, on London Underground machines. Some other ticket machines sell them, including those operated by c2c, London Overground and Scheidt & Bachmann (S&B) ticket machines operated by Southern, Thameslink, Great Northern, South Western Railway, London Northwestern Railway and Greater Anglia (link to Kingston Ramblers).

London Underground ticket machines only sell London Underground / DLR only boundary tickets for any Travelcards, or all boundary tickets for Oyster Travelcards, which means if you have a paper Travelcard and want to extend it to a National Rail station outside the zones, you can’t do it at a London Underground operated station.

The demonstration below shows the procedure to buy a boundary zone ticket for a season Travelcard loaded on the Oyster card, the most common use case. To begin with, London Underground ticket machines have a prominent button to buy an extension ticket on the home page. Tap the button.

Afterwards, tap your Oyster card, and enter your destination. Destinations within the Network Railcard area should be available, but if not, you will need to use your Travelcard to travel a National Rail interchange first, and buy the extension ticket from a National Rail ticket machine. If a boundary fare is not available to your destination, you will need to buy from the last station within the covered zones, e.g. if your Travelcard covers Zones 1-5, and you need to go to Birmingham International, you need to buy a ticket from Hatch Lane. A boundary ticket, if available, offers a greater flexibility as you can choose any boundary station for your journey instead of the one shown on the ticket. For example, a Boundary Zone 6 – Guildford return ticket, with route Any Permitted, used in combination with a Freedom Pass, allows you to travel out of the zones via Surbiton and return via Coulsdon South, which cannot be done with a ticket from a named station.

Add your railcards (if any), then choose the ticket you want.

Pay for the ticket. It looks like this.

This is a London Underground ticket from Willesden Green to Maidenhead, boundary zone 2 extension off-peak. It can be used with a Zones 1-2 Travelcard on a through Elizabeth line train from Bond Street to Maidenhead without exiting and re-entering at the boundary station.

Background information

The following is the rule which allows the use of extension fares in combination with a Travelcard.

14. Using a Combination of Tickets
    14.1 Some Tickets specifically exclude their use in conjunction with other Tickets. This will
    be made clear in the terms and conditions when buying such Tickets
    14.2 Unless Condition 14.1 applies, you may use a combination of two or more Tickets
    to make a journey provided that the train services you use Call at the station(s) where
    you change from one Ticket to another.
    14.3 Unless Condition 14.1 applies, if you are using a Season Ticket, daily Zonal Ticket, or
    another area based Ticket such as a concessionary pass, ranger, or rover, in
    conjunction with another Ticket and the last station at which one Ticket is valid and the
    first station that the other Ticket is valid are the same, then the train does not need to
    Call at that station for your combination to be valid.

National Rail Conditions of Travel, February 2022

The intention of the rule is that a season ticket / Travelcard / Freedom Pass holder should not need to double-pay for the part of the journey covered by the season ticket, while disallowing tickets intended for intermediate travel on slow trains being used on a non-stop fast train. Furthermore, there are specialised fares, called Travelcard extension fares, or boundary fares, created specifically for the purpose to make a through journey across the zonal boundary. These fares are usually (but not always) cheaper than the point-to-point fares between London and the same station outside the fare zones.

For example, a standard class London Paddington – Maidenhead Off-Peak Day Return costs £14.80, but if you already hold a Zones 1-6 Travelcard, you can buy a fare from Boundary Zone 6 (corresponding to the outermost zone covered by your Travelcard) instead, which only costs £7.00, and use it in combination with your Travelcard to make the journey on any trains on the route, regardless if it stops anywhere or not.

However, these boundary fares are not widely available from all sales channels. Only a limited number of websites and ticket machines can sell them, otherwise they can be bought at staffed ticket offices. This has led to passengers buying a ticket for their whole journey, paying more than they should have paid by buying a boundary fare instead. A class action lawsuit against Southeastern, South Western Railway and Govia Thameslink Railway (Thameslink, Southern and Great Northern) is ongoing as a result.

Most online retailers don’t sell boundary fares. Train companies which sell these tickets online include c2c and Avanti West Coast. They can be accessed by typing the word “boundary” and choosing the outer zone your Travelcard is valid into the search box. Independent retailer Trainsplit also sells them by allowing you to enter your Travelcard held into the advanced settings.

Ticket machines which sell boundary fares include S&B ticket machines operated by Thameslink, Southern, Great Northern, South Western Railway, London Northwestern Railway, Greater Anglia, however, those operated by Southeastern or GWR, although using the same software, have this function disabled. Ticket machines operated by c2c, London Overground, Elizabeth line and London Underground also sell boundary fares.