diff --git a/src/main/java/com/MeetMate/user/UserService.java b/src/main/java/com/MeetMate/user/UserService.java
index eca34b2..f478655 100644
--- a/src/main/java/com/MeetMate/user/UserService.java
+++ b/src/main/java/com/MeetMate/user/UserService.java
@@ -34,17 +34,17 @@ public GetResponse getUserByEmail(String token) {
     Optional<User> userOptional = userRepository.findUserByEmail(email);
 
     User user =
-        userRepository
-            .findUserByEmail(email)
-            .orElseThrow(() -> new EntityNotFoundException("User does not exist"));
+            userRepository
+                    .findUserByEmail(email)
+                    .orElseThrow(() -> new EntityNotFoundException("User does not exist"));
 
     return GetResponse.builder()
-        .id(user.getId())
-        .name(user.getName())
-        .created_at(user.getCreatedAt())
-        .email(user.getEmail())
-        .role(user.getRole())
-        .build();
+            .id(user.getId())
+            .name(user.getName())
+            .created_at(user.getCreatedAt())
+            .email(user.getEmail())
+            .role(user.getRole())
+            .build();
   }
 
   public List<User> getAllUsers() {
@@ -57,31 +57,36 @@ public void registerNewUser(MultiValueMap<String, String> data) throws NameAlrea
     String name = data.getFirst("name");
     String password = data.getFirst("password");
     String role = data.getFirst("role");
-    long associatedCompany = Long.parseLong(data.getFirst("associatedCompany"));
-    UserRole userRole;
-
-    if (role == null
-        || role.isEmpty())
-      userRole = UserRole.CLIENT;
-    else
-      userRole = UserRole.valueOf(role);
-
-    if (email == null
-        || email.isEmpty()
-        || password == null
-        || password.isEmpty()
-        || name == null
-        || name.isEmpty()) throw new IllegalArgumentException("Required argument is missing");
-
-    if (userRepository.findUserByEmail(email).isPresent())
+    Long associatedCompany = null;
+    String associatedCompanyStr = data.getFirst("associatedCompany");
+    if (associatedCompanyStr != null && !associatedCompanyStr.isEmpty()) {
+      try {
+        associatedCompany = Long.parseLong(associatedCompanyStr);
+      } catch (NumberFormatException e) {
+        throw new IllegalArgumentException("Invalid associatedCompany value", e);
+      }
+    }
+    UserRole userRole = (role == null || role.isEmpty()) ? UserRole.CLIENT : UserRole.valueOf(role);
+
+    if (email == null || email.isEmpty() || password == null || password.isEmpty() || name == null || name.isEmpty()) {
+      throw new IllegalArgumentException("Required argument is missing");
+    }
+
+    if (userRepository.findUserByEmail(email).isPresent()) {
       throw new NameAlreadyBoundException("Email already taken");
+    }
 
     User user = new User(name, email, passwordEncoder.encode(password), userRole);
 
     switch (userRole) {
-      case COMPANY_OWNER, COMPANY_MEMBER -> user.setAssociatedCompany(associatedCompany);
-      case CLIENT -> user.setAssociatedCompany(-1);
-      default -> throw new IllegalStateException(role + "is invalid!");
+      case COMPANY_OWNER, COMPANY_MEMBER -> {
+        if (associatedCompany == null) {
+          throw new IllegalArgumentException("associatedCompany is required for COMPANY_OWNER and COMPANY_MEMBER roles");
+        }
+        user.setAssociatedCompany(associatedCompany);
+      }
+      case CLIENT -> user.setAssociatedCompany(-1L);
+      default -> throw new IllegalStateException(role + " is invalid!");
     }
 
     userRepository.save(user);
@@ -94,9 +99,9 @@ public void updateUser(String token, MultiValueMap<String, String> data) {
     String password = passwordEncoder.encode(data.getFirst("password"));
 
     User user =
-        userRepository
-            .findUserByEmail(email)
-            .orElseThrow(() -> new EntityNotFoundException("User does not exist."));
+            userRepository
+                    .findUserByEmail(email)
+                    .orElseThrow(() -> new EntityNotFoundException("User does not exist."));
 
     if (password != null) user.setPassword(password);
     if (name != null) user.setName(name);
@@ -110,39 +115,39 @@ public AuthenticationResponse authenticateUser(MultiValueMap<String, String> dat
     authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(email, password));
 
     User user =
-        userRepository
-            .findUserByEmail(email)
-            .orElseThrow(() -> new EntityNotFoundException("User does not exist"));
+            userRepository
+                    .findUserByEmail(email)
+                    .orElseThrow(() -> new EntityNotFoundException("User does not exist"));
 
     String token = jwtService.generateAccessToken(user);
     String refresh = jwtService.generateRefreshToken(user);
     user.setRefreshToken(refresh);
     long exp =
-        jwtService.extractClaim(token, Claims::getExpiration).getTime()
-            / 1000; // expiration time in seconds
+            jwtService.extractClaim(token, Claims::getExpiration).getTime()
+                    / 1000; // expiration time in seconds
 
     return AuthenticationResponse.builder()
-        .access_Token(token)
-        .expires_at(exp)
-        .refresh_Token(refresh)
-        .build();
+            .access_Token(token)
+            .expires_at(exp)
+            .refresh_Token(refresh)
+            .build();
   }
 
   @Transactional
   public RefreshResponse refreshAccessToken(String refreshToken) {
     String email = jwtService.extractUserEmail(refreshToken);
     User user =
-        userRepository
-            .findUserByEmail(email)
-            .orElseThrow(() -> new EntityNotFoundException("User does not exist"));
+            userRepository
+                    .findUserByEmail(email)
+                    .orElseThrow(() -> new EntityNotFoundException("User does not exist"));
 
     if (!refreshToken.equals(user.getRefreshToken()))
       throw new IllegalStateException("Refresh token is invalid");
 
     String token = jwtService.generateAccessToken(user);
     long exp =
-        jwtService.extractClaim(token, Claims::getExpiration).getTime()
-            / 1000; // expiration time in seconds
+            jwtService.extractClaim(token, Claims::getExpiration).getTime()
+                    / 1000; // expiration time in seconds
 
     return RefreshResponse.builder().access_Token(token).expires_at(exp).build();
   }
@@ -151,9 +156,9 @@ public RefreshResponse refreshAccessToken(String refreshToken) {
   public void deleteUser(String token) {
     String email = jwtService.extractUserEmail(token);
     User user =
-        userRepository
-            .findUserByEmail(email)
-            .orElseThrow(() -> new EntityNotFoundException("User does not exist."));
+            userRepository
+                    .findUserByEmail(email)
+                    .orElseThrow(() -> new EntityNotFoundException("User does not exist."));
 
     userRepository.deleteByEmail(email);
   }