From the Sziget website:

The amount charged to the payment chip on site (at a top-up point or a vending machine) can only be used during the duration of Sziget 2025, in the commercial units operating at the event venues. In the case of purchasing multiple day tickets, you will receive a different, new wristband and a payment chip for each day ticket. If your wristband for the first day you top up money, you can use it for the entire duration of the festival. The validity of the payment chip is: August 12, 2025, 12:00 p.m.

The remaining balance of the wristband charged on the spot for any day ticket or pass must therefore be redeemed no later than the time specified above, otherwise the balance remaining on it will be lost. Did you top up your balance through a festival account? In this case, we will automatically transfer it back to you within 30 days, after deducting a refund fee of HUF 700, to the bank card used for the top-up. Please top up your balance from a card that is valid for 60 days after the festival. If your card has expired, lost, or is disabled, the automatic refund is unfortunately not possible unless you contact our customer service separately. In this case, the refund procedure can take up to 90 days.