diff --git a/src/Traits/Contact.php b/src/Traits/Contact.php
index b3aa068..b9ff01f 100644
--- a/src/Traits/Contact.php
+++ b/src/Traits/Contact.php
@@ -183,6 +183,39 @@ public function bulkCreateContacts(array $data = [], string $version = 'v1'): mi
         return $this->execute();
     }
 
+    /**
+     * Bulk creates or updates contacts, with their nested records, for a specified API version.
+     *
+     * Each contact is identified by its `contact_number`: one the platform does not hold is
+     * created, one it holds is updated. Nested products and bank accounts are matched by `id`,
+     * then by the caller's own `local_identifier` scoped to that contact, and created when
+     * neither matches — which is what makes this usable before the caller knows any platform
+     * ids at all. `bulkUpdateContact` cannot do that: it skips any nested record with no `id`.
+     *
+     * A product may name a bank account created in the same request through
+     * `contact_bank_account_local_identifier`, since that account has no id yet.
+     *
+     * @param  array  $data  (Optional) An associative array with a `contacts` key holding the contacts
+     *                       to upsert. Keys and values match the contact model's attributes.
+     * @param  string  $version  (Optional) The version of the API to target. Defaults to 'v1'.
+     * @return mixed The response from the API, shaped as `success` and `errors` keyed by the index
+     *               each contact was sent at — the same shape the other bulk endpoints return.
+     *
+     * @throws \Exception
+     */
+    public function bulkUpsertContacts(array $data = [], string $version = 'v1'): mixed
+    {
+        $this->init();
+        $this->setVersion($version);
+        $this->setData([
+            'json' => $data,
+        ]);
+        $this->setEndpoint('contacts/bulkUpsert');
+        $this->setRequestType('PUT');
+
+        return $this->execute();
+    }
+
     /**
      * Retrieves the allowed statuses for contacts.
      *
diff --git a/tests/Traits/ContactTest.php b/tests/Traits/ContactTest.php
index 7d619d2..941686b 100644
--- a/tests/Traits/ContactTest.php
+++ b/tests/Traits/ContactTest.php
@@ -105,6 +105,43 @@
     expect($result)->toBe($expectedResult);
 });
 
+test('bulkUpsertContacts calls expected methods and returns result', function () {
+    $mock = $this->getMockBuilder(PaymentPlatformAPI::class)
+        ->onlyMethods(['init', 'setVersion', 'setData', 'setEndpoint', 'setRequestType', 'execute'])
+        ->getMock();
+
+    $data = ['contacts' => [['contact_number' => '0000000005012']]];
+    $version = 'v3.0';
+
+    $mock->expects($this->once())->method('init')->willReturnSelf();
+    $mock->expects($this->once())->method('setVersion')->with($version)->willReturnSelf();
+    $mock->expects($this->once())->method('setData')->with(['json' => $data])->willReturnSelf();
+    $mock->expects($this->once())->method('setEndpoint')->with('contacts/bulkUpsert')->willReturnSelf();
+    // PUT, not POST: an upsert is idempotent, so it matches bulkUpdate rather than bulkCreate.
+    $mock->expects($this->once())->method('setRequestType')->with('PUT')->willReturnSelf();
+
+    $expectedResult = 'upsert-contacts-result';
+    $mock->expects($this->once())->method('execute')->willReturn($expectedResult);
+
+    $result = $mock->bulkUpsertContacts($data, $version);
+    expect($result)->toBe($expectedResult);
+});
+
+test('bulkUpsertContacts defaults to v1', function () {
+    $mock = $this->getMockBuilder(PaymentPlatformAPI::class)
+        ->onlyMethods(['init', 'setVersion', 'setData', 'setEndpoint', 'setRequestType', 'execute'])
+        ->getMock();
+
+    $mock->expects($this->once())->method('setVersion')->with('v1')->willReturnSelf();
+    $mock->method('init')->willReturnSelf();
+    $mock->method('setData')->willReturnSelf();
+    $mock->method('setEndpoint')->willReturnSelf();
+    $mock->method('setRequestType')->willReturnSelf();
+    $mock->method('execute')->willReturn(null);
+
+    $mock->bulkUpsertContacts([]);
+});
+
 test('createContact calls expected methods and returns result', function () {
     $mock = $this->getMockBuilder(PaymentPlatformAPI::class)
         ->onlyMethods(['init', 'setVersion', 'setData', 'setEndpoint', 'setRequestType', 'execute'])