If you're using a payment processor that isn't supported by Final Pay or an existing payment extension, you can still accept payments by setting up a custom payment method. While not integrated with Final, this option allows you to handle payments externally and mark them manually within your flows.
Custom Payment comes with its own element and action in Build, so you can still trigger and record payments as part of the POS experience. However, refunds to the original payment method won’t be possible through Final, since the transaction occurred outside the system.