There are two conditions for a fee payment to be fully valid:
If a payment does not relate to a pending European patent application (e.g. it relates to a patent application already deemed to be withdrawn) or to pending proceedings, there is no legal basis for the payment. In these cases, the amount paid must be refunded.
If the payment is made before or on the due date and if, no later than that date, the legal basis ceases to exist (e.g. because the patent application is deemed to be withdrawn or is withdrawn), the amount paid is to be refunded. For the designation fee and renewal fees see A‑X, 5.2.2 and 5.2.4, respectively. Fees paid after the due date and before expiry of the time limit for payment are refunded only if there is a particular reason for a refund (see A‑X, 10.2).