diff --git a/src/Core/AdminConsole/OrganizationFeatures/OrganizationUsers/UpdateOrganizationUserCommand.cs b/src/Core/AdminConsole/OrganizationFeatures/OrganizationUsers/UpdateOrganizationUserCommand.cs
index 657cc6c54d..4aaecef29f 100644
--- a/src/Core/AdminConsole/OrganizationFeatures/OrganizationUsers/UpdateOrganizationUserCommand.cs
+++ b/src/Core/AdminConsole/OrganizationFeatures/OrganizationUsers/UpdateOrganizationUserCommand.cs
@@ -63,10 +63,10 @@ public class UpdateOrganizationUserCommand : IUpdateOrganizationUserCommand
         List<CollectionAccessSelection>? collectionAccess, IEnumerable<Guid>? groupAccess)
     {
         // Avoid multiple enumeration
-        collectionAccess = collectionAccess?.ToList();
+        var collectionAccessList = collectionAccess?.ToList() ?? [];
         groupAccess = groupAccess?.ToList();
 
-        if (organizationUser.Id.Equals(default(Guid)))
+        if (organizationUser.Id.Equals(Guid.Empty))
         {
             throw new BadRequestException("Invite the user first.");
         }
@@ -93,9 +93,9 @@ public class UpdateOrganizationUserCommand : IUpdateOrganizationUserCommand
             }
         }
 
-        if (collectionAccess?.Any() == true)
+        if (collectionAccessList.Count != 0)
         {
-            await ValidateCollectionAccessAsync(originalOrganizationUser, collectionAccess.ToList());
+            await ValidateCollectionAccessAsync(originalOrganizationUser, collectionAccessList);
         }
 
         if (groupAccess?.Any() == true)
@@ -111,14 +111,15 @@ public class UpdateOrganizationUserCommand : IUpdateOrganizationUserCommand
         await _organizationService.ValidateOrganizationCustomPermissionsEnabledAsync(organizationUser.OrganizationId, organizationUser.Type);
 
         if (organizationUser.Type != OrganizationUserType.Owner &&
-            !await _hasConfirmedOwnersExceptQuery.HasConfirmedOwnersExceptAsync(organizationUser.OrganizationId, new[] { organizationUser.Id }))
+            !await _hasConfirmedOwnersExceptQuery.HasConfirmedOwnersExceptAsync(organizationUser.OrganizationId,
+                [organizationUser.Id]))
         {
             throw new BadRequestException("Organization must have at least one confirmed owner.");
         }
 
-        if (collectionAccess?.Count > 0)
+        if (collectionAccessList?.Count > 0)
         {
-            var invalidAssociations = collectionAccess.Where(cas => cas.Manage && (cas.ReadOnly || cas.HidePasswords));
+            var invalidAssociations = collectionAccessList.Where(cas => cas.Manage && (cas.ReadOnly || cas.HidePasswords));
             if (invalidAssociations.Any())
             {
                 throw new BadRequestException("The Manage property is mutually exclusive and cannot be true while the ReadOnly or HidePasswords properties are also true.");
@@ -140,7 +141,7 @@ public class UpdateOrganizationUserCommand : IUpdateOrganizationUserCommand
             }
         }
 
-        await _organizationUserRepository.ReplaceAsync(organizationUser, collectionAccess);
+        await _organizationUserRepository.ReplaceAsync(organizationUser, collectionAccessList);
 
         if (groupAccess != null)
         {
diff --git a/src/Core/AdminConsole/OrganizationFeatures/Organizations/CloudOrganizationSignUpCommand.cs b/src/Core/AdminConsole/OrganizationFeatures/Organizations/CloudOrganizationSignUpCommand.cs
index 57cfd1e60f..60e090de2a 100644
--- a/src/Core/AdminConsole/OrganizationFeatures/Organizations/CloudOrganizationSignUpCommand.cs
+++ b/src/Core/AdminConsole/OrganizationFeatures/Organizations/CloudOrganizationSignUpCommand.cs
@@ -24,8 +24,7 @@ namespace Bit.Core.AdminConsole.OrganizationFeatures.Organizations;
 
 public record SignUpOrganizationResponse(
     Organization Organization,
-    OrganizationUser OrganizationUser,
-    Collection DefaultCollection);
+    OrganizationUser OrganizationUser);
 
 public interface ICloudOrganizationSignUpCommand
 {
@@ -34,7 +33,6 @@ public interface ICloudOrganizationSignUpCommand
 
 public class CloudOrganizationSignUpCommand(
     IOrganizationUserRepository organizationUserRepository,
-    IFeatureService featureService,
     IOrganizationBillingService organizationBillingService,
     IPaymentService paymentService,
     IPolicyService policyService,
@@ -144,7 +142,7 @@ public class CloudOrganizationSignUpCommand(
                 // TODO: add reference events for SmSeats and Service Accounts - see AC-1481
             });
 
-        return new SignUpOrganizationResponse(returnValue.organization, returnValue.organizationUser, returnValue.defaultCollection);
+        return new SignUpOrganizationResponse(returnValue.organization, returnValue.organizationUser);
     }
 
     public void ValidatePasswordManagerPlan(Plan plan, OrganizationUpgrade upgrade)
diff --git a/src/Core/AdminConsole/OrganizationFeatures/Organizations/Interfaces/IOrganizationDeleteCommand.cs b/src/Core/AdminConsole/OrganizationFeatures/Organizations/Interfaces/IOrganizationDeleteCommand.cs
index fc4de42bed..8153a10958 100644
--- a/src/Core/AdminConsole/OrganizationFeatures/Organizations/Interfaces/IOrganizationDeleteCommand.cs
+++ b/src/Core/AdminConsole/OrganizationFeatures/Organizations/Interfaces/IOrganizationDeleteCommand.cs
@@ -1,4 +1,5 @@
 using Bit.Core.AdminConsole.Entities;
+using Bit.Core.Exceptions;
 
 namespace Bit.Core.AdminConsole.OrganizationFeatures.Organizations.Interfaces;
 
diff --git a/src/Core/AdminConsole/OrganizationFeatures/Organizations/Interfaces/IOrganizationInitiateDeleteCommand.cs b/src/Core/AdminConsole/OrganizationFeatures/Organizations/Interfaces/IOrganizationInitiateDeleteCommand.cs
index a8d211f245..867d41e7db 100644
--- a/src/Core/AdminConsole/OrganizationFeatures/Organizations/Interfaces/IOrganizationInitiateDeleteCommand.cs
+++ b/src/Core/AdminConsole/OrganizationFeatures/Organizations/Interfaces/IOrganizationInitiateDeleteCommand.cs
@@ -1,4 +1,5 @@
 using Bit.Core.AdminConsole.Entities;
+using Bit.Core.Exceptions;
 
 namespace Bit.Core.AdminConsole.OrganizationFeatures.Organizations.Interfaces;
 
diff --git a/src/Core/AdminConsole/OrganizationFeatures/Policies/PolicyValidators/TwoFactorAuthenticationPolicyValidator.cs b/src/Core/AdminConsole/OrganizationFeatures/Policies/PolicyValidators/TwoFactorAuthenticationPolicyValidator.cs
index 04984b17be..c757a65913 100644
--- a/src/Core/AdminConsole/OrganizationFeatures/Policies/PolicyValidators/TwoFactorAuthenticationPolicyValidator.cs
+++ b/src/Core/AdminConsole/OrganizationFeatures/Policies/PolicyValidators/TwoFactorAuthenticationPolicyValidator.cs
@@ -73,6 +73,11 @@ public class TwoFactorAuthenticationPolicyValidator : IPolicyValidator
     {
         var organization = await _organizationRepository.GetByIdAsync(organizationId);
 
+        if (organization is null)
+        {
+            return;
+        }
+
         var currentActiveRevocableOrganizationUsers =
             (await _organizationUserRepository.GetManyDetailsByOrganizationAsync(organizationId))
             .Where(ou => ou.Status != OrganizationUserStatusType.Invited &&
@@ -90,9 +95,11 @@ public class TwoFactorAuthenticationPolicyValidator : IPolicyValidator
         var revocableUsersWithTwoFactorStatus =
             await _twoFactorIsEnabledQuery.TwoFactorIsEnabledAsync(currentActiveRevocableOrganizationUsers);
 
-        var nonCompliantUsers = revocableUsersWithTwoFactorStatus.Where(x => !x.twoFactorIsEnabled);
+        var nonCompliantUsers = revocableUsersWithTwoFactorStatus
+            .Where(x => !x.twoFactorIsEnabled)
+            .ToArray();
 
-        if (!nonCompliantUsers.Any())
+        if (nonCompliantUsers.Length == 0)
         {
             return;
         }
diff --git a/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationUserRepository.cs b/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationUserRepository.cs
index 0165360099..28e2f1a9e4 100644
--- a/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationUserRepository.cs
+++ b/src/Infrastructure.EntityFramework/AdminConsole/Repositories/OrganizationUserRepository.cs
@@ -249,6 +249,7 @@ public class OrganizationUserRepository : Repository<Core.Entities.OrganizationU
         }
     }
 
+#nullable enable
     public async Task<(OrganizationUserUserDetails? OrganizationUser, ICollection<CollectionAccessSelection> Collections)> GetDetailsByIdWithCollectionsAsync(Guid id)
     {
         var organizationUserUserDetails = await GetDetailsByIdAsync(id);
@@ -269,6 +270,7 @@ public class OrganizationUserRepository : Repository<Core.Entities.OrganizationU
             return (organizationUserUserDetails, collections);
         }
     }
+#nullable disable
 
     public async Task<OrganizationUserOrganizationDetails> GetDetailsByUserAsync(Guid userId, Guid organizationId, OrganizationUserStatusType? status = null)
     {