Customers

One customer per billing account

You may create a Customer before Checkout, or let Checkout resolve/create it. Use a stable account id from your application as external_id to prevent duplicates.

const customer = await fetch(
  `${apiUrl}/public/v2/customers`,
  {
    method: "POST",
    headers: apiHeaders,
    body: JSON.stringify({
      external_id: account.id,
      email: account.ownerEmail,
      name: account.name,
    }),
  },
).then((res) => res.json())

Store the mapping

Store customer.data.id next to your internal billing account. Active Customer email and external_id are unique inside an Organization, but external_id should remain your stable mapping.

Idempotency

If a request times out, inspect the mapping you already store before creating another customer. Your system should guarantee one VietBilling customer per billing account.