diff --git a/Civi/Api4/Generic/AbstractAction.php b/Civi/Api4/Generic/AbstractAction.php
index 050fd5a6ca43..0957b696b1a7 100644
--- a/Civi/Api4/Generic/AbstractAction.php
+++ b/Civi/Api4/Generic/AbstractAction.php
@@ -456,30 +456,6 @@ public function reflect() {
     return $this->_reflection;
   }
 
-  /**
-   * Validates required fields for actions which create a new object.
-   *
-   * @param $values
-   * @return array
-   * @throws \API_Exception
-   */
-  protected function checkRequiredFields($values) {
-    $unmatched = [];
-    foreach ($this->entityFields() as $fieldName => $fieldInfo) {
-      if (!isset($values[$fieldName]) || $values[$fieldName] === '') {
-        if (!empty($fieldInfo['required']) && !isset($fieldInfo['default_value'])) {
-          $unmatched[] = $fieldName;
-        }
-        elseif (!empty($fieldInfo['required_if'])) {
-          if ($this->evaluateCondition($fieldInfo['required_if'], ['values' => $values])) {
-            $unmatched[] = $fieldName;
-          }
-        }
-      }
-    }
-    return $unmatched;
-  }
-
   /**
    * Replaces pseudoconstants in input values
    *
diff --git a/Civi/Api4/Generic/AbstractCreateAction.php b/Civi/Api4/Generic/AbstractCreateAction.php
index 153e26ce6f59..71f63613ed65 100644
--- a/Civi/Api4/Generic/AbstractCreateAction.php
+++ b/Civi/Api4/Generic/AbstractCreateAction.php
@@ -31,6 +31,8 @@
  */
 abstract class AbstractCreateAction extends AbstractAction {
 
+  use \Civi\Api4\Generic\Traits\CheckRequiredTrait;
+
   /**
    * Field values to set for the new $ENTITY.
    *
@@ -61,11 +63,7 @@ public function addValue(string $fieldName, $value) {
    * @throws \API_Exception
    */
   protected function validateValues() {
-    // FIXME: There should be a protocol to report a full list of errors... Perhaps a subclass of API_Exception?
-    $unmatched = $this->checkRequiredFields($this->getValues());
-    if ($unmatched) {
-      throw new \API_Exception("Mandatory values missing from Api4 {$this->getEntityName()}::{$this->getActionName()}: " . implode(", ", $unmatched), "mandatory_missing", ["fields" => $unmatched]);
-    }
+    $this->checkRequired([$this->values]);
     $e = new ValidateValuesEvent($this, [$this->getValues()], new \CRM_Utils_LazyArray(function () {
       return [['old' => NULL, 'new' => $this->getValues()]];
     }));
diff --git a/Civi/Api4/Generic/AbstractSaveAction.php b/Civi/Api4/Generic/AbstractSaveAction.php
index 29f329cc661e..3a5998888537 100644
--- a/Civi/Api4/Generic/AbstractSaveAction.php
+++ b/Civi/Api4/Generic/AbstractSaveAction.php
@@ -42,6 +42,8 @@
  */
 abstract class AbstractSaveAction extends AbstractAction {
 
+  use \Civi\Api4\Generic\Traits\CheckRequiredTrait;
+
   /**
    * Array of $ENTITIES to save.
    *
@@ -95,16 +97,10 @@ public function __construct($entityName, $actionName, $idField = 'id') {
    * @throws \API_Exception
    */
   protected function validateValues() {
-    // FIXME: There should be a protocol to report a full list of errors... Perhaps a subclass of API_Exception?
-    $unmatched = [];
-    foreach ($this->records as $record) {
-      if (empty($record[$this->idField])) {
-        $unmatched = array_unique(array_merge($unmatched, $this->checkRequiredFields($record)));
-      }
-    }
-    if ($unmatched) {
-      throw new \API_Exception("Mandatory values missing from Api4 {$this->getEntityName()}::{$this->getActionName()}: " . implode(", ", $unmatched), "mandatory_missing", ["fields" => $unmatched]);
-    }
+    $this->checkRequired($this->records, function($record) {
+      return empty($record[$this->idField]);
+    });
+
     $e = new ValidateValuesEvent($this, $this->records, new \CRM_Utils_LazyArray(function() {
       $existingIds = array_column($this->records, $this->idField);
       $existing = civicrm_api4($this->getEntityName(), 'get', [
diff --git a/Civi/Api4/Generic/Traits/CheckRequiredTrait.php b/Civi/Api4/Generic/Traits/CheckRequiredTrait.php
new file mode 100644
index 000000000000..ded6f7940a8f
--- /dev/null
+++ b/Civi/Api4/Generic/Traits/CheckRequiredTrait.php
@@ -0,0 +1,68 @@
+<?php
+namespace Civi\Api4\Generic\Traits;
+
+/**
+ * The CheckRequiredTrait provides a helper, `checkRequired()`, to determine if required fields are specified.
+ * This would be consulted when adding a new record.
+ *
+ * This should be moved to a subscriber ('civi.api4.validate') that reports issues via `addError()`. However, for the moment, it
+ * relies on things which are in the action class (e.g. entityFields(), evaluateCondition(), $isNew<=>$idField), and it can't
+ * be fully extracted until those are changed.
+ *
+ * @deprecated
+ */
+trait CheckRequiredTrait {
+
+  abstract protected static function getEntityName();
+
+  abstract protected static function getActionName();
+
+  abstract protected function entityFields();
+
+  abstract protected function evaluateCondition($expr, $vars);
+
+  /**
+   * When creating new records, ensure that the 'required' fields are present. Throws an exception if any fields are missing.
+   *
+   * @param array $records
+   * @param callable|TRUE $isNew A function that can distinguish whether the record is new, or constant TRUE if all records are new.
+   * @throws \API_Exception
+   */
+  protected function checkRequired($records, $isNew = TRUE) {
+    $unmatched = [];
+
+    foreach ($records as $record) {
+      if ($isNew === TRUE || $isNew($record)) {
+        $unmatched = array_unique(array_merge($unmatched, $this->checkRequiredFieldValues($record)));
+      }
+    }
+    if ($unmatched) {
+      throw new \API_Exception("Mandatory values missing from Api4 {$this->getEntityName()}::{$this->getActionName()}: " . implode(", ", $unmatched), "mandatory_missing", ["fields" => $unmatched]);
+    }
+  }
+
+  /**
+   * Validates required fields for actions which create a new object.
+   *
+   * @param $values
+   * @return array
+   * @throws \API_Exception
+   */
+  protected function checkRequiredFieldValues($values) {
+    $unmatched = [];
+    foreach ($this->entityFields() as $fieldName => $fieldInfo) {
+      if (!isset($values[$fieldName]) || $values[$fieldName] === '') {
+        if (!empty($fieldInfo['required']) && !isset($fieldInfo['default_value'])) {
+          $unmatched[] = $fieldName;
+        }
+        elseif (!empty($fieldInfo['required_if'])) {
+          if ($this->evaluateCondition($fieldInfo['required_if'], ['values' => $values])) {
+            $unmatched[] = $fieldName;
+          }
+        }
+      }
+    }
+    return $unmatched;
+  }
+
+}