Valid for a single, one-way, uninterrupted trip started on the indicated day, on the route sections of the suburban railway lines outside the administrative boundaries of Budapest. Advance purchase is possible up to 30 days before the starting day of validity at ticket offices, customer service centres, ticket vending machines (TVMs) and via even the MÁV app. Ticket purchase on board is possible without penalty fare payment if the passenger boards at a stop where there is no ticket office or TVM available. For travelling within the city boundaries, passengers require a valid pass or a validated ticket. The ticket along with the certificate or ID proving eligibility for a discount must be handed over to the inspector.
Refund rule: tickets purchased in advance are refundable prior to the start of validity, if the value of the ticket exceeds the handling fee.
Please find more information at the following link concerning Suburban Railway Fares.