diff --git a/src/app/Http/Controllers/API/V4/Admin/UsersController.php b/src/app/Http/Controllers/API/V4/Admin/UsersController.php
--- a/src/app/Http/Controllers/API/V4/Admin/UsersController.php
+++ b/src/app/Http/Controllers/API/V4/Admin/UsersController.php
@@ -90,6 +90,31 @@
                     $result->push($owner);
                 }
             }
+        // A mollie customer ID
+        } elseif (substr($search, 0, 4) == 'cst_') {
+            $setting = \App\WalletSetting::where(
+                [
+                    'key' => 'mollie_id',
+                    'value' => $search
+                ]
+            )->first();
+
+            if ($setting) {
+                if ($wallet = $setting->wallet) {
+                    if ($owner = $wallet->owner()->withTrashed()->first()) {
+                        $result->push($owner);
+                    }
+                }
+            }
+        // A mollie transaction ID
+        } elseif (substr($search, 0, 3) == 'tr_') {
+            $payment = \App\Payment::find($search);
+
+            if ($payment) {
+                if ($owner = $payment->wallet->owner()->withTrashed()->first()) {
+                    $result->push($owner);
+                }
+            }
         } elseif (!empty($search)) {
             $wallet = Wallet::find($search);
 
diff --git a/src/tests/Feature/Controller/Admin/UsersTest.php b/src/tests/Feature/Controller/Admin/UsersTest.php
--- a/src/tests/Feature/Controller/Admin/UsersTest.php
+++ b/src/tests/Feature/Controller/Admin/UsersTest.php
@@ -189,6 +189,24 @@
         $plan = \App\Plan::where('title', 'group')->first();
         $user->assignPlan($plan, $domain);
         $user->setAliases(['alias@testsearch.com']);
+
+        $wallet = $user->wallets()->first();
+        $wallet->setSetting('mollie_id', 'cst_nonsense');
+
+        \App\Payment::create(
+            [
+                'id' => 'tr_nonsense',
+                'wallet_id' => $wallet->id,
+                'status' => 'paid',
+                'amount' => 1337,
+                'description' => 'nonsense transaction for testing',
+                'provider' => 'self',
+                'type' => 'oneoff',
+                'currency' => 'CHF',
+                'currency_amount' => 1337
+            ]
+        );
+
         Queue::fake();
         $user->delete();
 
@@ -224,6 +242,39 @@
         $this->assertSame($user->id, $json['list'][0]['id']);
         $this->assertSame($user->email, $json['list'][0]['email']);
         $this->assertTrue($json['list'][0]['isDeleted']);
+
+        $response = $this->actingAs($admin)->get("api/v4/users?search={$wallet->id}");
+        $response->assertStatus(200);
+
+        $json = $response->json();
+
+        $this->assertSame(1, $json['count']);
+        $this->assertCount(1, $json['list']);
+        $this->assertSame($user->id, $json['list'][0]['id']);
+        $this->assertSame($user->email, $json['list'][0]['email']);
+        $this->assertTrue($json['list'][0]['isDeleted']);
+
+        $response = $this->actingAs($admin)->get("api/v4/users?search=tr_nonsense");
+        $response->assertStatus(200);
+
+        $json = $response->json();
+
+        $this->assertSame(1, $json['count']);
+        $this->assertCount(1, $json['list']);
+        $this->assertSame($user->id, $json['list'][0]['id']);
+        $this->assertSame($user->email, $json['list'][0]['email']);
+        $this->assertTrue($json['list'][0]['isDeleted']);
+
+        $response = $this->actingAs($admin)->get("api/v4/users?search=cst_nonsense");
+        $response->assertStatus(200);
+
+        $json = $response->json();
+
+        $this->assertSame(1, $json['count']);
+        $this->assertCount(1, $json['list']);
+        $this->assertSame($user->id, $json['list'][0]['id']);
+        $this->assertSame($user->email, $json['list'][0]['email']);
+        $this->assertTrue($json['list'][0]['isDeleted']);
     }
 
     /**