This is another of the great benefits for Oyster users over paper tickets, yet some of those benefits are not explained very well on the TfL site. If you have a travelcard season stored on your Oyster and want to travel beyond the covered zones then you can use your pay-as-you-go balance to pay for the extra bit (or bits). All you have to do is touch in and out at both ends of your journey. This is very important, however, because the system still needs to know what journey you have made to charge you correctly.
How much will it cost
You only pay for travel in the zones not covered by your travelcard. Unlike paper extension tickets which can only be issued from the outer boundary of a zone, Oyster also works from the inner boundary as well. Thus if you have a zone 2-4 travelcard and pop into Central London one evening you only pay for zone 1 single fares**. With paper you would be charged from the last zone 2 station. If you want to travel from zone 5 to zone 1 with a zone 2-4 travelcard it will charge you the cheaper of two methods: either a zone 5 single and a zone 1 single; or a zone 5-1 single (as if you didn’t have a travelcard).
** Note that there is a special arrangement when you hold a travelcard covering at least zone 2 and you make a through NR1+T journey covering zone 1. Rather than pay the inflated through zone 1 fare you will be charged the lower TfL-LU zone 1 fare. However, as with all things Oyster, even this rule has exceptions. If your first touch out in zone 1 is at a NR terminal you will be charged the higher NR1 zone 1 fare even if you then go onto the Underground. Conversely, if you want to make a journey starting in zone 1 using NR1 fares then you will save money if you can make an Underground journey first. For example, if you have a zone 2-6 travelcard and want to travel from Charing Cross to Crayford at 5pm you’ll save money taking the Underground to Waterloo first.
Things to watch out for
Oyster will charge you based on the whole journey you make, not just on the portion outside of your zones. So, if you have a zone 1-2 travelcard and start at Upton Park (z3) using the District/Jubilee line to Waterloo, then National Rail to Wandsworth Town in zone 2 it will charge you for zone 3 in a mixed NR1+T journey, even if your zone 3 travel was only on TfL. Most of the time this will only make a few pence difference, but it can be more. If your journey started in the evening peak then the first stage (Upton Park – Waterloo) is charged off-peak as it finishes in zone 1. But when you then continue your journey and touch out at Wandsworth Town it changes to a peak mixed NR1+T zone 3 journey. Armed with this knowledge there are two ways to get round it. First you can wait around at Waterloo until 40 minutes after your touch out from the Underground. This will mean that part two is a new journey fully covered by your travelcard. Alternatively you can touch onto a bus and then get off again. Bus travel is free with any travelcard, but touching on a bus will break the journey in two.
What happens if I forget to touch in or out?
Remember that at all times you can be charged a penalty fare or considered for prosecution if you are outside of the zones on your travelcard and not touched in. Having said that, this is what happens as far as your PAYG balance is concerned.
If you don’t touch in within your zones and then touch out outside of your zones you will be charged a reduced maximum fare which will not count towards any daily cap. Likewise if you touch in outside your zones and forget to touch out again at the end of your journey.
If you touch in or out within your zones but not when outside there will be no effect on your PAYG balance, but you can still be charged a penalty fare. This can even happen after you have passed the validators on your way out of the station.