How do I pay off my apple card
How do I pay off my Apple Card so I don’t get charged interest
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Payments are described in How to make Apple Card payments.
This paragraph seems to answer your question.
"Make a one-time payment
Watch the video to learn how to make a one-time payment on your Apple Card balance >
On your iPhone in the Wallet app, you can make an immediate one-time payment or you can schedule a one-time payment."