# Customer basics

A [customer resource](https://app.gitbook.com/s/x8fSFzVR3sg0TsNWwwVz/customers) allows you to store a customer's unique identifier, name, phone, email, shipping address, saved payment sources, tax identifiers, tax certificates, and other data.

This resource is especially useful in [registered checkouts](https://docs.digitalriver.com/digital-river-api/integration-options/checkouts/creating-checkouts/using-the-checkout-identifier#registered-checkouts-or-invoices).

For example, once you set a customer's `shipping.address`, you can retrieve these values during later [checkouts](https://docs.digitalriver.com/digital-river-api/integration-options/checkouts/creating-checkouts) and display them as an available option to the storefront customer. This often helps expedite the checkout process.

Additionally, if customers want to save a [reusable payment method](https://docs.digitalriver.com/digital-river-api/payments/supported-payment-methods) for future use, you can [attach the created payment source to their record](https://docs.digitalriver.com/digital-river-api/payments/payment-sources/using-the-source-identifier#attaching-sources-to-customers). When that same customer later initiates a [registered checkout](https://docs.digitalriver.com/digital-river-api/integration-options/checkouts/creating-checkouts/using-the-checkout-identifier#registered-checkouts-or-invoices), you can [retrieve a list of applicable payment methods](https://docs.digitalriver.com/digital-river-api/developer-resources/reference/digitalriver-object#retrieving-available-payment-methods) and then use this list to filter the customer's [reusable sources](https://docs.digitalriver.com/digital-river-api/payments/payment-sources#reusable-or-single-use) before displaying them in your GUI.

You can also use the resource to [set up and store a customer's tax-exempt data](https://docs.digitalriver.com/digital-river-api/customer-management/setting-tax-related-attributes).