Adds one payment to a metered order, to charge the customer for usage. The payment joins the order's schedule as a new scheduled payment.

A scheduled payment is a planned future collection on an instalment, subscription or metered order. It shows as one billing event in the order's payment timeline. A metered order has no schedule of its own: each payment you add here is one scheduled payment.

1. Send the product_id of a product on the order. Choose when to collect with process_date.
2. BillPro works out the amount from the product's price on this order, with its fees, discounts and tax. The currency is always the order's currency.
3. You get back the new scheduled payment, with status scheduled. Nothing is charged in this request.
4. BillPro collects it on its date. With now, the next collection run charges it. To charge it straight away and see the result, execute it with the returned id.

• Send amount to confirm the figure you showed. If it's off by more than one cent, you get a 422 with the right amount. It never changes the price.
• The product and your note are saved in the order's notes. They aren't stored on the payment.
• Only metered orders accept this request. Other order types return 422.
• There's no currency field. One sent is ignored.

To cancel the payment before it's collected, skip it.