Yes, your Zakat remains valid and successfully fulfilled. In the event a Zakat payer (muzakki) misses or delays their credit card repayment, whether intentionally or due to oversight, and a late penalty fee is incurred, it does not affect the validity of the Zakat transaction itself. However, muzakkis are strongly advised to plan their repayments carefully to avoid incurring late fees, which may involve elements of riba (interest) and lead to unnecessary financial distress.