WordPress at a glance
filter is not described

woocommerce_checkout_customer_id filter-hook . WC 1.0

Create a new customer account if needed.

Usage

add_filter( 'woocommerce_checkout_customer_id', 'filter_function_name_228' );
function filter_function_name_228( $data ){
	// filter...

	return $data;
}
$data(array)
Posted data.

Where the hook is called

WC_Checkout::process_customer()
woocommerce_checkout_customer_id
WC_Checkout::__get()
woocommerce_checkout_customer_id
WC_Checkout::create_order()
woocommerce_checkout_customer_id
woocommerce/includes/class-wc-checkout.php 1019
$customer_id = apply_filters( 'woocommerce_checkout_customer_id', get_current_user_id() );
woocommerce/includes/class-wc-checkout.php 157
return apply_filters( 'woocommerce_checkout_customer_id', get_current_user_id() );
woocommerce/includes/class-wc-checkout.php 372
$order->set_customer_id( apply_filters( 'woocommerce_checkout_customer_id', get_current_user_id() ) );

Where in WP core the hook is used WooCommerce

Usage not found.