We can derive contactID from stripe customer

Civi/StripeImport/Charge.php

@@ -104,6 +104,24 @@ class Charge extends Base {
       $this->setDescription('Stripe: Manual import via API');
     }
 
+    if (empty($this->getContactID())) {
+      // Derive contact ID from stripe customer
+      if (empty(\CRM_Stripe_Api::getObjectParam('customer_id', $stripeCharge))) {
+        throw new \Exception('Missing customer_id in Stripe Charge. Cannot derive contact ID');
+      }
+      $stripeCustomer = \Civi\Api4\StripeCustomer::get(FALSE)
+        ->addWhere('customer_id', '=', \CRM_Stripe_Api::getObjectParam('customer_id', $stripeCharge))
+        ->addWhere('processor_id', '=', $this->getPaymentProcessorID())
+        ->addClause('OR', ['currency', 'IS EMPTY'], ['currency', '=', \CRM_Stripe_Api::getObjectParam('customer_id', $stripeCharge)])
+        ->addOrderBy('currency', 'DESC')
+        ->execute()
+        ->first();
+      if (empty($stripeCustomer)) {
+        throw new \Exception('Stripe Customer: ' . \CRM_Stripe_Api::getObjectParam('customer_id', $stripeCharge) . ' not found in CiviCRM. Cannot derive contact ID');
+      }
+      $this->setContactID($stripeCustomer['contact_id']);
+    }
+
     // Check for a subscription.
     if (isset($stripeInvoice)) {
       $subscriptionID = \CRM_Stripe_Api::getObjectParam('subscription_id', $stripeInvoice);

api/v3/Stripe/Importcharge.php

@@ -21,8 +21,9 @@ function _civicrm_api3_stripe_importcharge_spec(&$spec) {
   $spec['ppid']['type'] = CRM_Utils_Type::T_INT;
   $spec['ppid']['api.required'] = TRUE;
   $spec['contact_id']['title'] = E::ts('Contact ID');
+  $spec['contact_id']['description'] = E::ts('If not specified this will be determined from the "customer" on the charge - a StripeCustomer record must exist in CiviCRM');
   $spec['contact_id']['type'] = CRM_Utils_Type::T_INT;
-  $spec['contact_id']['api.required'] = TRUE;
+  $spec['contact_id']['api.required'] = FALSE;
   $spec['charge']['title'] = E::ts('Stripe Charge ID');
   $spec['charge']['description'] = E::ts('The Charge ID to import');
   $spec['charge']['type'] = CRM_Utils_Type::T_STRING;