The FOREIGN KEY requirement in Entity Framework clashed with the INSERT statement.

I have already tested this scenario and it works great:

    class Program
    {
        static void Main(string[] args)
        {
            PMSCatalogEntities entities = new PMSCatalogEntities();

            Subscription subs = new Subscription();
            subs.Id = Guid.NewGuid();
            subs.Date = DateTime.Now;
            subs.PaymentId = 1;

            entities.Subscriptions.Add(subs);
            entities.SaveChanges();
        }
    }

    public class PMSCatalogEntities : DbContext
    {
        public DbSet<Subscription> Subscriptions { get; set; }

        public DbSet<Payment> Payments { get; set; }

    }

    public class Subscription
    {
        public Guid Id { get; set; }

        public DateTime Date { get; set; }

        public Payment Payment { get; set; }

        public int PaymentId { get; set; }
    }

    public class Payment
    {
        public int Id { get; set; }

        public string Type { get; set; }
    }

And on the DB

TABLE [dbo].[Payments](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Type] [nvarchar](max) NULL,

TABLE [dbo].[Subscriptions](
    [Id] [uniqueidentifier] NOT NULL,
    [Date] [datetime] NOT NULL,
    [PaymentId] [int] NOT NULL,

The only thing I have to be sure is that a Payment with Id 1 for this example is persisted on the Payments table, and it works like a charm!!