diff --git a/includes/class-wc-stripe-customer.php b/includes/class-wc-stripe-customer.php
new file mode 100644
index 0000000..7666dcb
--- /dev/null
+++ b/includes/class-wc-stripe-customer.php
@@ -0,0 +1,726 @@
+<?php
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * WC_Stripe_Customer class.
+ *
+ * Represents a Stripe Customer.
+ */
+class WC_Stripe_Customer {
+
+	/**
+	 * String prefix for Stripe payment methods request transient.
+	 */
+	const PAYMENT_METHODS_TRANSIENT_KEY = 'stripe_payment_methods_';
+
+	/**
+	 * Queryable Stripe payment method types.
+	 */
+	const STRIPE_PAYMENT_METHODS = [
+		WC_Stripe_UPE_Payment_Method_CC::STRIPE_ID,
+		WC_Stripe_UPE_Payment_Method_Sepa::STRIPE_ID,
+	];
+
+	/**
+	 * Stripe customer ID
+	 *
+	 * @var string
+	 */
+	private $id = '';
+
+	/**
+	 * WP User ID
+	 *
+	 * @var integer
+	 */
+	private $user_id = 0;
+
+	/**
+	 * Data from API
+	 *
+	 * @var array
+	 */
+	private $customer_data = [];
+
+	/**
+	 * Constructor
+	 *
+	 * @param int $user_id The WP user ID
+	 */
+	public function __construct( $user_id = 0 ) {
+		if ( $user_id ) {
+			$this->set_user_id( $user_id );
+			$this->set_id( $this->get_id_from_meta( $user_id ) );
+		}
+	}
+
+	/**
+	 * Get Stripe customer ID.
+	 *
+	 * @return string
+	 */
+	public function get_id() {
+		return $this->id;
+	}
+
+	/**
+	 * Set Stripe customer ID.
+	 *
+	 * @param [type] $id [description]
+	 */
+	public function set_id( $id ) {
+		// Backwards compat for customer ID stored in array format. (Pre 3.0)
+		if ( is_array( $id ) && isset( $id['customer_id'] ) ) {
+			$id = $id['customer_id'];
+
+			$this->update_id_in_meta( $id );
+		}
+
+		$this->id = wc_clean( $id );
+	}
+
+	/**
+	 * User ID in WordPress.
+	 *
+	 * @return int
+	 */
+	public function get_user_id() {
+		return absint( $this->user_id );
+	}
+
+	/**
+	 * Set User ID used by WordPress.
+	 *
+	 * @param int $user_id
+	 */
+	public function set_user_id( $user_id ) {
+		$this->user_id = absint( $user_id );
+	}
+
+	/**
+	 * Get user object.
+	 *
+	 * @return WP_User
+	 */
+	protected function get_user() {
+		return $this->get_user_id() ? get_user_by( 'id', $this->get_user_id() ) : false;
+	}
+
+	/**
+	 * Store data from the Stripe API about this customer
+	 */
+	public function set_customer_data( $data ) {
+		$this->customer_data = $data;
+	}
+
+	/**
+	 * Generates the customer request, used for both creating and updating customers.
+	 *
+	 * @param  array $args Additional arguments (optional).
+	 * @return array
+	 */
+	protected function generate_customer_request( $args = [] ) {
+		$billing_email = isset( $_POST['billing_email'] ) ? filter_var( wp_unslash( $_POST['billing_email'] ), FILTER_SANITIZE_EMAIL ) : '';
+		$user          = $this->get_user();
+
+		if ( $user ) {
+			$billing_first_name = get_user_meta( $user->ID, 'billing_first_name', true );
+			$billing_last_name  = get_user_meta( $user->ID, 'billing_last_name', true );
+
+			// If billing first name does not exists try the user first name.
+			if ( empty( $billing_first_name ) ) {
+				$billing_first_name = get_user_meta( $user->ID, 'first_name', true );
+			}
+
+			// If billing last name does not exists try the user last name.
+			if ( empty( $billing_last_name ) ) {
+				$billing_last_name = get_user_meta( $user->ID, 'last_name', true );
+			}
+
+			// translators: %1$s First name, %2$s Second name, %3$s Username.
+			$description = sprintf( __( 'Name: %1$s %2$s, Username: %3$s', 'woocommerce-gateway-stripe' ), $billing_first_name, $billing_last_name, $user->user_login );
+
+			$defaults = [
+				'email'       => $user->user_email,
+				'description' => $description,
+			];
+
+			$billing_full_name = trim( $billing_first_name . ' ' . $billing_last_name );
+			if ( ! empty( $billing_full_name ) ) {
+				$defaults['name'] = $billing_full_name;
+			}
+		} else {
+			$billing_first_name = isset( $_POST['billing_first_name'] ) ? filter_var( wp_unslash( $_POST['billing_first_name'] ), FILTER_SANITIZE_STRING ) : ''; // phpcs:ignore WordPress.Security.NonceVerification
+			$billing_last_name  = isset( $_POST['billing_last_name'] ) ? filter_var( wp_unslash( $_POST['billing_last_name'] ), FILTER_SANITIZE_STRING ) : ''; // phpcs:ignore WordPress.Security.NonceVerification
+
+			// translators: %1$s First name, %2$s Second name.
+			$description = sprintf( __( 'Name: %1$s %2$s, Guest', 'woocommerce-gateway-stripe' ), $billing_first_name, $billing_last_name );
+
+			$defaults = [
+				'email'       => $billing_email,
+				'description' => $description,
+			];
+
+			$billing_full_name = trim( $billing_first_name . ' ' . $billing_last_name );
+			if ( ! empty( $billing_full_name ) ) {
+				$defaults['name'] = $billing_full_name;
+			}
+		}
+
+		$metadata                      = [];
+		$defaults['metadata']          = apply_filters( 'wc_stripe_customer_metadata', $metadata, $user );
+		$defaults['preferred_locales'] = $this->get_customer_preferred_locale( $user );
+
+		return wp_parse_args( $args, $defaults );
+	}
+
+	/**
+	 * Create a customer via API.
+	 *
+	 * @param array $args
+	 * @return WP_Error|int
+	 */
+	public function create_customer( $args = [] ) {
+		$args     = $this->generate_customer_request( $args );
+		$response = WC_Stripe_API::request( apply_filters( 'wc_stripe_create_customer_args', $args ), 'customers' );
+
+		if ( ! empty( $response->error ) ) {
+			throw new WC_Stripe_Exception( print_r( $response, true ), $response->error->message );
+		}
+
+		$this->set_id( $response->id );
+		$this->clear_cache();
+		$this->set_customer_data( $response );
+
+		if ( $this->get_user_id() ) {
+			$this->update_id_in_meta( $response->id );
+		}
+
+		do_action( 'woocommerce_stripe_add_customer', $args, $response );
+
+		return $response->id;
+	}
+
+	/**
+	 * Updates the Stripe customer through the API.
+	 *
+	 * @param array $args     Additional arguments for the request (optional).
+	 * @param bool  $is_retry Whether the current call is a retry (optional, defaults to false). If true, then an exception will be thrown instead of further retries on error.
+	 *
+	 * @return string Customer ID
+	 *
+	 * @throws WC_Stripe_Exception
+	 */
+	public function update_customer( $args = [], $is_retry = false ) {
+		if ( empty( $this->get_id() ) ) {
+			throw new WC_Stripe_Exception( 'id_required_to_update_user', __( 'Attempting to update a Stripe customer without a customer ID.', 'woocommerce-gateway-stripe' ) );
+		}
+
+		$args     = $this->generate_customer_request( $args );
+		$args     = apply_filters( 'wc_stripe_update_customer_args', $args );
+		$response = WC_Stripe_API::request( $args, 'customers/' . $this->get_id() );
+
+		if ( ! empty( $response->error ) ) {
+			if ( $this->is_no_such_customer_error( $response->error ) && ! $is_retry ) {
+				// This can happen when switching the main Stripe account or importing users from another site.
+				// If not already retrying, recreate the customer and then try updating it again.
+				$this->recreate_customer();
+				return $this->update_customer( $args, true );
+			}
+
+			throw new WC_Stripe_Exception( print_r( $response, true ), $response->error->message );
+		}
+
+		$this->clear_cache();
+		$this->set_customer_data( $response );
+
+		do_action( 'woocommerce_stripe_update_customer', $args, $response );
+
+		return $this->get_id();
+	}
+
+	/**
+	 * Updates existing Stripe customer or creates new customer for User through API.
+	 *
+	 * @param array $args     Additional arguments for the request (optional).
+	 * @param bool  $is_retry Whether the current call is a retry (optional, defaults to false). If true, then an exception will be thrown instead of further retries on error.
+	 *
+	 * @return string Customer ID
+	 *
+	 * @throws WC_Stripe_Exception
+	 */
+	public function update_or_create_customer( $args = [], $is_retry = false ) {
+		if ( empty( $this->get_id() ) ) {
+			return $this->recreate_customer();
+		} else {
+			return $this->update_customer( $args, true );
+		}
+	}
+
+	/**
+	 * Checks to see if error is of invalid request
+	 * error and it is no such customer.
+	 *
+	 * @since 4.1.2
+	 * @param array $error
+	 */
+	public function is_no_such_customer_error( $error ) {
+		return (
+			$error &&
+			'invalid_request_error' === $error->type &&
+			preg_match( '/No such customer/i', $error->message )
+		);
+	}
+
+	/**
+	 * Checks to see if error is of invalid request
+	 * error and it is no such customer.
+	 *
+	 * @since 4.5.6
+	 * @param array $error
+	 * @return bool
+	 */
+	public function is_source_already_attached_error( $error ) {
+		return (
+			$error &&
+			'invalid_request_error' === $error->type &&
+			preg_match( '/already been attached to a customer/i', $error->message )
+		);
+	}
+
+	/**
+	 * Add a source for this stripe customer.
+	 *
+	 * @param string $source_id
+	 * @return WP_Error|int
+	 */
+	public function add_source( $source_id ) {
+		$response = WC_Stripe_API::retrieve( 'sources/' . $source_id );
+
+		if ( ! empty( $response->error ) || is_wp_error( $response ) ) {
+			return $response;
+		}
+
+		// Add token to WooCommerce.
+		$wc_token = false;
+
+		if ( $this->get_user_id() && class_exists( 'WC_Payment_Token_CC' ) ) {
+			if ( ! empty( $response->type ) ) {
+				switch ( $response->type ) {
+					case 'alipay':
+						break;
+					case 'sepa_debit':
+						$wc_token = new WC_Payment_Token_SEPA();
+						$wc_token->set_token( $response->id );
+						$wc_token->set_gateway_id( 'stripe_sepa' );
+						$wc_token->set_last4( $response->sepa_debit->last4 );
+						break;
+					default:
+						if ( 'source' === $response->object && 'card' === $response->type ) {
+							$wc_token = new WC_Payment_Token_CC();
+							$wc_token->set_token( $response->id );
+							$wc_token->set_gateway_id( 'stripe' );
+							$wc_token->set_card_type( strtolower( $response->card->brand ) );
+							$wc_token->set_last4( $response->card->last4 );
+							$wc_token->set_expiry_month( $response->card->exp_month );
+							$wc_token->set_expiry_year( $response->card->exp_year );
+						}
+						break;
+				}
+			} else {
+				// Legacy.
+				$wc_token = new WC_Payment_Token_CC();
+				$wc_token->set_token( $response->id );
+				$wc_token->set_gateway_id( 'stripe' );
+				$wc_token->set_card_type( strtolower( $response->brand ) );
+				$wc_token->set_last4( $response->last4 );
+				$wc_token->set_expiry_month( $response->exp_month );
+				$wc_token->set_expiry_year( $response->exp_year );
+			}
+
+			$wc_token->set_user_id( $this->get_user_id() );
+			$wc_token->save();
+		}
+
+		$this->clear_cache();
+
+		do_action( 'woocommerce_stripe_add_source', $this->get_id(), $wc_token, $response, $source_id );
+
+		return $response->id;
+	}
+
+	/**
+	 * Attaches a source to the Stripe customer.
+	 *
+	 * @param string $source_id The ID of the new source.
+	 * @return object|WP_Error Either a source object, or a WP error.
+	 */
+	public function attach_source( $source_id ) {
+		if ( ! $this->get_id() ) {
+			$this->set_id( $this->create_customer() );
+		}
+
+		$response = WC_Stripe_API::request(
+			[
+				'source' => $source_id,
+			],
+			'customers/' . $this->get_id() . '/sources'
+		);
+
+		if ( ! empty( $response->error ) ) {
+			// It is possible the WC user once was linked to a customer on Stripe
+			// but no longer exists. Instead of failing, lets try to create a
+			// new customer.
+			if ( $this->is_no_such_customer_error( $response->error ) ) {
+				$this->recreate_customer();
+				return $this->attach_source( $source_id );
+			} elseif ( $this->is_source_already_attached_error( $response->error ) ) {
+				return WC_Stripe_API::request( [], 'sources/' . $source_id, 'GET' );
+			} else {
+				return $response;
+			}
+		} elseif ( empty( $response->id ) ) {
+			return new WP_Error( 'error', __( 'Unable to add payment source.', 'woocommerce-gateway-stripe' ) );
+		} else {
+			return $response;
+		}
+	}
+
+	/**
+	 * Get a customers saved sources using their Stripe ID.
+	 *
+	 * @param  string $customer_id
+	 * @return array
+	 */
+	public function get_sources() {
+		if ( ! $this->get_id() ) {
+			return [];
+		}
+
+		$sources = get_transient( 'stripe_sources_' . $this->get_id() );
+
+		if ( false === $sources ) {
+			$response = WC_Stripe_API::request(
+				[
+					'limit' => 100,
+				],
+				'customers/' . $this->get_id() . '/sources',
+				'GET'
+			);
+
+			if ( ! empty( $response->error ) ) {
+				return [];
+			}
+
+			if ( is_array( $response->data ) ) {
+				$sources = $response->data;
+			}
+
+			set_transient( 'stripe_sources_' . $this->get_id(), $sources, DAY_IN_SECONDS );
+		}
+
+		return empty( $sources ) ? [] : $sources;
+	}
+
+	/**
+	 * Gets saved payment methods for a customer using Intentions API.
+	 *
+	 * @param string $payment_method_type Stripe ID of payment method type
+	 *
+	 * @return array
+	 */
+	public function get_payment_methods( $payment_method_type ) {
+		if ( ! $this->get_id() ) {
+			return [];
+		}
+
+		$payment_methods = get_transient( self::PAYMENT_METHODS_TRANSIENT_KEY . $payment_method_type . $this->get_id() );
+
+		if ( false === $payment_methods ) {
+			$params   = WC_Stripe_UPE_Payment_Method_Sepa::STRIPE_ID === $payment_method_type ? '?expand[]=data.sepa_debit.generated_from.charge&expand[]=data.sepa_debit.generated_from.setup_attempt' : '';
+			$response = WC_Stripe_API::request(
+				[
+					'customer' => $this->get_id(),
+					'type'     => $payment_method_type,
+					'limit'    => 100, // Maximum allowed value.
+				],
+				'payment_methods' . $params,
+				'GET'
+			);
+
+			if ( ! empty( $response->error ) ) {
+				return [];
+			}
+
+			if ( is_array( $response->data ) ) {
+				$payment_methods = $response->data;
+			}
+
+			set_transient( self::PAYMENT_METHODS_TRANSIENT_KEY . $payment_method_type . $this->get_id(), $payment_methods, DAY_IN_SECONDS );
+		}
+
+		return empty( $payment_methods ) ? [] : $payment_methods;
+	}
+
+	/**
+	 * Delete a source from stripe.
+	 *
+	 * @param string $source_id
+	 */
+	public function delete_source( $source_id ) {
+		if ( ! $this->get_id() ) {
+			return false;
+		}
+
+		$response = WC_Stripe_API::request( [], 'customers/' . $this->get_id() . '/sources/' . sanitize_text_field( $source_id ), 'DELETE' );
+
+		$this->clear_cache();
+
+		if ( empty( $response->error ) ) {
+			do_action( 'wc_stripe_delete_source', $this->get_id(), $response );
+
+			return true;
+		}
+
+		return false;
+	}
+
+	/**
+	 * Detach a payment method from stripe.
+	 *
+	 * @param string $payment_method_id
+	 */
+	public function detach_payment_method( $payment_method_id ) {
+		if ( ! $this->get_id() ) {
+			return false;
+		}
+
+		$response = WC_Stripe_API::request( [], "payment_methods/$payment_method_id/detach", 'POST' );
+
+		$this->clear_cache();
+
+		if ( empty( $response->error ) ) {
+			do_action( 'wc_stripe_detach_payment_method', $this->get_id(), $response );
+
+			return true;
+		}
+
+		return false;
+	}
+
+	/**
+	 * Set default source in Stripe
+	 *
+	 * @param string $source_id
+	 */
+	public function set_default_source( $source_id ) {
+		$response = WC_Stripe_API::request(
+			[
+				'default_source' => sanitize_text_field( $source_id ),
+			],
+			'customers/' . $this->get_id(),
+			'POST'
+		);
+
+		$this->clear_cache();
+
+		if ( empty( $response->error ) ) {
+			do_action( 'wc_stripe_set_default_source', $this->get_id(), $response );
+
+			return true;
+		}
+
+		return false;
+	}
+
+	/**
+	 * Set default payment method in Stripe
+	 *
+	 * @param string $payment_method_id
+	 */
+	public function set_default_payment_method( $payment_method_id ) {
+		$response = WC_Stripe_API::request(
+			[
+				'invoice_settings' => [
+					'default_payment_method' => sanitize_text_field( $payment_method_id ),
+				],
+			],
+			'customers/' . $this->get_id(),
+			'POST'
+		);
+
+		$this->clear_cache();
+
+		if ( empty( $response->error ) ) {
+			do_action( 'wc_stripe_set_default_payment_method', $this->get_id(), $response );
+
+			return true;
+		}
+
+		return false;
+	}
+
+	/**
+	 * Deletes caches for this users cards.
+	 */
+	public function clear_cache() {
+		delete_transient( 'stripe_sources_' . $this->get_id() );
+		delete_transient( 'stripe_customer_' . $this->get_id() );
+		foreach ( self::STRIPE_PAYMENT_METHODS as $payment_method_type ) {
+			delete_transient( self::PAYMENT_METHODS_TRANSIENT_KEY . $payment_method_type . $this->get_id() );
+		}
+		$this->customer_data = [];
+	}
+
+	/**
+	 * Retrieves the Stripe Customer ID from the user meta.
+	 *
+	 * @param  int $user_id The ID of the WordPress user.
+	 * @return string|bool  Either the Stripe ID or false.
+	 */
+	public function get_id_from_meta( $user_id ) {
+		return get_user_option( '_stripe_customer_id', $user_id );
+	}
+
+	/**
+	 * Updates the current user with the right Stripe ID in the meta table.
+	 *
+	 * @param string $id The Stripe customer ID.
+	 */
+	public function update_id_in_meta( $id ) {
+		update_user_option( $this->get_user_id(), '_stripe_customer_id', $id, false );
+	}
+
+	/**
+	 * Deletes the user ID from the meta table with the right key.
+	 */
+	public function delete_id_from_meta() {
+		delete_user_option( $this->get_user_id(), '_stripe_customer_id', false );
+	}
+
+	/**
+	 * Recreates the customer for this user.
+	 *
+	 * @return string ID of the new Customer object.
+	 */
+	private function recreate_customer() {
+		$this->delete_id_from_meta();
+		return $this->create_customer();
+	}
+
+	/**
+	 * Get the customer's preferred locale based on the user or site setting.
+	 *
+	 * @param object $user The user being created/modified.
+	 * @return array The matched locale string wrapped in an array, or empty default.
+	 */
+	public function get_customer_preferred_locale( $user ) {
+		$locale = $this->get_customer_locale( $user );
+
+		// Options based on Stripe locales.
+		// https://support.stripe.com/questions/language-options-for-customer-emails
+		$stripe_locales = [
+			'ar'    => 'ar-AR',
+			'da_DK' => 'da-DK',
+			'de_DE' => 'de-DE',
+			'en'    => 'en-US',
+			'es_ES' => 'es-ES',
+			'es_CL' => 'es-419',
+			'es_AR' => 'es-419',
+			'es_CO' => 'es-419',
+			'es_PE' => 'es-419',
+			'es_UY' => 'es-419',
+			'es_PR' => 'es-419',
+			'es_GT' => 'es-419',
+			'es_EC' => 'es-419',
+			'es_MX' => 'es-419',
+			'es_VE' => 'es-419',
+			'es_CR' => 'es-419',
+			'fi'    => 'fi-FI',
+			'fr_FR' => 'fr-FR',
+			'he_IL' => 'he-IL',
+			'it_IT' => 'it-IT',
+			'ja'    => 'ja-JP',
+			'nl_NL' => 'nl-NL',
+			'nn_NO' => 'no-NO',
+			'pt_BR' => 'pt-BR',
+			'sv_SE' => 'sv-SE',
+		];
+
+		$preferred = isset( $stripe_locales[ $locale ] ) ? $stripe_locales[ $locale ] : 'en-US';
+		return [ $preferred ];
+	}
+
+	/**
+	 * Gets the customer's locale/language based on their setting or the site settings.
+	 *
+	 * @param object $user The user we're wanting to get the locale for.
+	 * @return string The locale/language set in the user profile or the site itself.
+	 */
+	public function get_customer_locale( $user ) {
+		// If we have a user, get their locale with a site fallback.
+		return ( $user ) ? get_user_locale( $user->ID ) : get_locale();
+	}
+
+	/**
+	 * Given a WC_Order or WC_Customer, returns an array representing a Stripe customer object.
+	 * At least one parameter has to not be null.
+	 *
+	 * @param WC_Order    $wc_order    The Woo order to parse.
+	 * @param WC_Customer $wc_customer The Woo customer to parse.
+	 *
+	 * @return array Customer data.
+	 */
+	public static function map_customer_data( WC_Order $wc_order = null, WC_Customer $wc_customer = null ) {
+		if ( null === $wc_customer && null === $wc_order ) {
+			return [];
+		}
+
+		// Where available, the order data takes precedence over the customer.
+		$object_to_parse = isset( $wc_order ) ? $wc_order : $wc_customer;
+		$name            = $object_to_parse->get_billing_first_name() . ' ' . $object_to_parse->get_billing_last_name();
+		$description     = '';
+		if ( null !== $wc_customer && ! empty( $wc_customer->get_username() ) ) {
+			// We have a logged in user, so add their username to the customer description.
+			// translators: %1$s Name, %2$s Username.
+			$description = sprintf( __( 'Name: %1$s, Username: %2$s', 'woocommerce-gateway-stripe' ), $name, $wc_customer->get_username() );
+		} else {
+			// Current user is not logged in.
+			// translators: %1$s Name.
+			$description = sprintf( __( 'Name: %1$s, Guest', 'woocommerce-gateway-stripe' ), $name );
+		}
+
+		$data = [
+			'name'        => $name,
+			'description' => $description,
+			'email'       => $object_to_parse->get_billing_email(),
+			'phone'       => $object_to_parse->get_billing_phone(),
+			'address'     => [
+				'line1'       => $object_to_parse->get_billing_address_1(),
+				'line2'       => $object_to_parse->get_billing_address_2(),
+				'postal_code' => $object_to_parse->get_billing_postcode(),
+				'city'        => $object_to_parse->get_billing_city(),
+				'state'       => $object_to_parse->get_billing_state(),
+				'country'     => $object_to_parse->get_billing_country(),
+			],
+		];
+
+		if ( ! empty( $object_to_parse->get_shipping_postcode() ) ) {
+			$data['shipping'] = [
+				'name'    => $object_to_parse->get_shipping_first_name() . ' ' . $object_to_parse->get_shipping_last_name(),
+				'address' => [
+					'line1'       => $object_to_parse->get_shipping_address_1(),
+					'line2'       => $object_to_parse->get_shipping_address_2(),
+					'postal_code' => $object_to_parse->get_shipping_postcode(),
+					'city'        => $object_to_parse->get_shipping_city(),
+					'state'       => $object_to_parse->get_shipping_state(),
+					'country'     => $object_to_parse->get_shipping_country(),
+				],
+			];
+		}
+
+		return $data;
+	}
+}