diff --git a/api/app/src/FixtureFactory/PreRegistrationFactory.php b/api/app/src/FixtureFactory/PreRegistrationFactory.php
index 3c26f0bf70..2a0f6b5145 100644
--- a/api/app/src/FixtureFactory/PreRegistrationFactory.php
+++ b/api/app/src/FixtureFactory/PreRegistrationFactory.php
@@ -20,13 +20,14 @@ public function __construct(private PreRegistrationDTOFactory $preRegistrationFa
     public function create(array $data): PreRegistration
     {
         $caseNumber = str_pad((string) rand(1, 99999999), 8, '0', STR_PAD_LEFT);
-        $deputyNumber = str_pad((string) rand(1, 999999999999), 12, '0', STR_PAD_LEFT);
+        $generateDeputyUidIfNotSet = '7'.str_pad((string) rand(1, 99999999), 11, '0', STR_PAD_LEFT);
+        $deputyUid = array_key_exists('deputyUid', $data) && strval($data['deputyUid']) ? strval($data['deputyUid']) : $generateDeputyUidIfNotSet;
         $reportType = 'ndr' == $data['reportType'] ? 'OPG102' : $data['reportType'];
 
         $dto = (new LayDeputyshipDto())
             ->setCaseNumber($data['caseNumber'] ?? $caseNumber)
             ->setClientSurname($data['clientLastName'] ?? 'Smith')
-            ->setDeputyUid($deputyNumber)
+            ->setDeputyUid($deputyUid)
             ->setDeputyAddress1($data['deputyAddress1'] ?? 'Victoria Park')
             ->setDeputyAddress2($data['deputyAddress2'] ?? 'Fakeville')
             ->setDeputyAddress3($data['deputyAddress3'] ?? 'Pretendham')
diff --git a/api/app/src/FixtureFactory/UserFactory.php b/api/app/src/FixtureFactory/UserFactory.php
index ac5394a223..17ac319f5a 100644
--- a/api/app/src/FixtureFactory/UserFactory.php
+++ b/api/app/src/FixtureFactory/UserFactory.php
@@ -40,7 +40,8 @@ public function create(array $data): User
             ->setAddressPostcode(isset($data['postCode']) ? $data['postCode'] : 'SW1')
             ->setAddressCountry('GB')
             ->setRoleName($roleName)
-            ->setAgreeTermsUse(true);
+            ->setAgreeTermsUse(true)
+            ->setDeputyUid(User::TYPE_LAY === $data['deputyType'] ? $data['deputyUid'] : null);
 
         if ('true' === $data['activated'] || true === $data['activated']) {
             $user->setPassword($this->passwordHasher->hashPassword($user, 'DigidepsPass1234'));
@@ -135,10 +136,12 @@ public function createCoDeputy(User $originalDeputy, Client $client, array $data
             ->setActive($data['activated'])
             ->setRegistrationDate(new \DateTime())
             ->setCoDeputyClientConfirmed(true)
-            ->setActive(true);
+            ->setActive(true)
+            ->setDeputyUid('7'.str_pad((string) rand(1, 99999999), 11, '0', STR_PAD_LEFT));
 
         if ('true' === $data['activated'] || true === $data['activated']) {
-            $user2->setPassword($this->passwordHasher->hashPassword($user2, 'DigidepsPass1234'));
+            $user2->setPassword($this->passwordHasher->hashPassword($user2, 'DigidepsPass1234'))
+                  ->setIsPrimary(true);
         } else {
             $user2->setActive(false);
         }
diff --git a/api/app/src/v2/Fixture/Controller/FixtureController.php b/api/app/src/v2/Fixture/Controller/FixtureController.php
index a0c1e0e0b9..485b9f91ef 100644
--- a/api/app/src/v2/Fixture/Controller/FixtureController.php
+++ b/api/app/src/v2/Fixture/Controller/FixtureController.php
@@ -83,6 +83,7 @@ public function createCourtOrderAction(Request $request)
                     'deputyLastName' => $deputy->getLastname(),
                     'deputyFirstName' => $deputy->getFirstName(),
                     'reportType' => $fromRequest['reportType'],
+                    'deputyUid' => $fromRequest['deputyUid'],
                 ]
             );
 
@@ -97,6 +98,7 @@ public function createCourtOrderAction(Request $request)
         }
 
         if (User::TYPE_LAY === $fromRequest['deputyType']) {
+            $deputy->setIsPrimary(true);
             $deputy->addClient($client);
         } else {
             $this->createOrgAndAttachParticipants($fromRequest, $deputy, $client);
@@ -114,6 +116,7 @@ public function createCourtOrderAction(Request $request)
                     'deputyLastName' => $coDeputy->getLastname(),
                     'deputyFirstName' => $coDeputy->getFirstName(),
                     'reportType' => $fromRequest['reportType'],
+                    'deputyUid' => $coDeputy->getDeputyUid(),
                 ]
             );
 
@@ -154,6 +157,7 @@ private function createDeputy($fromRequest): User
             'email' => $fromRequest['deputyEmail'],
             'activated' => $fromRequest['activated'],
             'coDeputyEnabled' => $fromRequest['coDeputyEnabled'],
+            'deputyUid' => $fromRequest['deputyUid'],
         ]);
 
         $this->em->persist($deputy);
@@ -252,7 +256,7 @@ private function buildDeputy(User $deputy, array $fromRequest)
             ->setFirstname($deputy->getFirstname())
             ->setLastname($deputy->getLastname())
             ->setEmail1($deputy->getEmail())
-            ->setDeputyUid($fromRequest['caseNumber'].mt_rand(1, 100))
+            ->setDeputyUid('70'.str_pad($fromRequest['caseNumber'].mt_rand(1, 100), 10))
             ->setAddress1($deputy->getAddress1())
             ->setAddressPostcode($deputy->getAddressPostcode())
             ->setPhoneMain($deputy->getPhoneMain());
diff --git a/api/app/tests/Unit/Controller/SelfRegisterControllerTest.php b/api/app/tests/Unit/Controller/SelfRegisterControllerTest.php
index d32cdacf12..dacd716cd4 100644
--- a/api/app/tests/Unit/Controller/SelfRegisterControllerTest.php
+++ b/api/app/tests/Unit/Controller/SelfRegisterControllerTest.php
@@ -737,7 +737,7 @@ private function generateDeputyPrimaryAccount()
             'data' => [
                 'firstname' => 'Sue',
                 'lastname' => 'Jones',
-                'email' => sprintf('firstdeputyaccount%s@example.com', rand(1, 20)),
+                'email' => sprintf('firstdeputy%s@example.com', $casenumber),
                 'postcode' => 'SW1',
                 'client_firstname' => 'John',
                 'client_lastname' => 'Smith',
diff --git a/client/app/src/Controller/Admin/FixtureController.php b/client/app/src/Controller/Admin/FixtureController.php
index e6e046b1a7..ee975effff 100644
--- a/client/app/src/Controller/Admin/FixtureController.php
+++ b/client/app/src/Controller/Admin/FixtureController.php
@@ -93,6 +93,7 @@ public function courtOrdersAction(Request $request)
             $courtDate = $request->get('court-date') ? new \DateTime($request->get('court-date')) : new \DateTime();
             $deputyEmail = $request->query->get('deputy-email', sprintf('original-%s-deputy-%s@fixture.com', strtolower($submitted['deputyType']), mt_rand(1000, 9999)));
             $caseNumber = $request->get('case-number', ClientHelpers::createValidCaseNumber());
+            $deputyUid = intval('7'.str_pad((string) mt_rand(1, 99999999), 11, '0', STR_PAD_LEFT));
 
             $response = $this->restClient->post('v2/fixture/court-order', json_encode([
                 'deputyType' => $submitted['deputyType'],
@@ -105,6 +106,7 @@ public function courtOrdersAction(Request $request)
                 'activated' => $submitted['activated'],
                 'orgSizeClients' => $submitted['orgSizeClients'],
                 'orgSizeUsers' => $submitted['orgSizeUsers'],
+                'deputyUid' => $deputyUid,
             ]));
 
             $query = ['query' => ['filter_by_ids' => implode(',', $response['deputyIds'])]];
diff --git a/client/app/src/Service/Client/Internal/ClientApi.php b/client/app/src/Service/Client/Internal/ClientApi.php
index 709a438a36..7704c39283 100644
--- a/client/app/src/Service/Client/Internal/ClientApi.php
+++ b/client/app/src/Service/Client/Internal/ClientApi.php
@@ -172,7 +172,7 @@ public function getWithUsersV2(int $clientId, array $includes = [])
     public function getById(int $clientId, array $includes = [])
     {
         return $this->restClient->get(
-            sprintf(self::GET_CLIENT_BY_ID_V2, $clientId),
+            sprintf(self::GET_CLIENT_BY_ID, $clientId),
             'Client',
             [
                 'client',