From Sunday the 6th of July 2014, all London buses are going cash free so you will no longer be able to use cash to pay for your bus fare.
Instead of cash, you can use an Oyster or contactless payment card to pay as you go, or a Travelcard. A single adult bus fare is £1.45 with Oyster or a contactless payment card. Only touch the card you want to use on the yellow card reader.
For more information please go to www.tfl.gov.uk/waystopay