Index: iknow-api/Data/AppDbContext.cs
===================================================================
--- iknow-api/Data/AppDbContext.cs	(revision ea405569ef29f56fbfc4d77708b6b3faf9286097)
+++ iknow-api/Data/AppDbContext.cs	(revision 8ee90bd3c5fa141766e0944837c6bc414d8b09c4)
@@ -290,13 +290,9 @@
                 e.HasKey(p => p.Id);
                 e.Property(p => p.Id).HasColumnName("id");
-                e.Property(p => p.UserId).HasColumnName("user_id");
                 e.Property(p => p.EnrollmentInfoId).HasColumnName("enrollment_id");
                 e.Property(p => p.Amount).HasColumnName("amount");
 
-                e.HasOne(p => p.User)
-                 .WithMany(u => u.Payments)
-                 .HasForeignKey(p => p.UserId)
-                 .OnDelete(DeleteBehavior.Cascade);
-
+                // No user_id: the student comes from the enrolment. Removing it
+                // was the BCNF fix from Phase 5 (enrolled_id -> user_id).
                 e.HasOne(p => p.EnrolledSemesters)
                  .WithMany(es => es.Users)
Index: iknow-api/Models/Payment.cs
===================================================================
--- iknow-api/Models/Payment.cs	(revision ea405569ef29f56fbfc4d77708b6b3faf9286097)
+++ iknow-api/Models/Payment.cs	(revision 8ee90bd3c5fa141766e0944837c6bc414d8b09c4)
@@ -1,16 +1,16 @@
-using System.ComponentModel.DataAnnotations.Schema;
-
 namespace iknow_api.Models
 {
+    /// <summary>
+    /// The student is reached through the enrolment: enrolled_id -> user_id.
+    /// A user_id here would be redundant and could contradict the enrolment,
+    /// which is the BCNF violation found during normalization (Phase 5).
+    /// </summary>
     public class Payment
     {
         public int Id { get; set; }
 
-        public int UserId { get; set; }
-        public User? User { get; set; }
         public int EnrollmentInfoId { get; set; }
         public int Amount { get; set; }
         public EnrolledSemesters? EnrolledSemesters { get; set; }
-
     }
 }
Index: iknow-api/Models/User.cs
===================================================================
--- iknow-api/Models/User.cs	(revision ea405569ef29f56fbfc4d77708b6b3faf9286097)
+++ iknow-api/Models/User.cs	(revision 8ee90bd3c5fa141766e0944837c6bc414d8b09c4)
@@ -28,7 +28,4 @@
         public ICollection<UserDocuments>? Documents { get; set; }
 
-        // Named for the relationship it carries: Users 1 --pays-- N Payment.
-        public ICollection<Payment>? Payments { get; set; }
-
         // Users 1 --submits-- N EnrolledSemesters
         public ICollection<EnrolledSemesters>? Enrolments { get; set; }