<p>Attaches a PaymentMethod object to a Customer.</p> <p>To attach a new PaymentMethod to a customer for future payments, we recommend you use a <a href="/docs/api/setup_intents">SetupIntent</a> or a PaymentIntent with <a href="/docs/api/payment_intents/create#create_payment_intent-setup_future_usage">setup_future_usage</a>. These approaches will perform any necessary steps to set up the PaymentMethod for future payments. Using the <code>/v1/payment_methods/:id/attach</code> endpoint without first using a SetupIntent or PaymentIntent with <code>setup_future_usage</code> does not optimize the PaymentMethod for future use, which makes later declines and payment friction more likely. See <a href="/docs/payments/payment-intents#future-usage">Optimizing cards for future payments</a> for more information about setting up future payments.</p> <p>To use this PaymentMethod as the default for invoice or subscription payments, set <a href="/docs/api/customers/update#update_customer-invoice_settings-default_payment_method"><code>invoice_settings.default_payment_method</code></a>, on the Customer to the PaymentMethod’s ID.</p>