diff --git a/LiteCharms.Features.MidrandBooks/Payments/PayfastService.cs b/LiteCharms.Features.MidrandBooks/Payments/PayfastService.cs
index 8aa1eec..8d440d8 100644
--- a/LiteCharms.Features.MidrandBooks/Payments/PayfastService.cs
+++ b/LiteCharms.Features.MidrandBooks/Payments/PayfastService.cs
@@ -147,23 +147,56 @@ public sealed partial class PayfastService(IDbContextFactory<MidrandBooksDbConte
     {
         var pfOutput = new StringBuilder();
 
-        foreach (var kvp in data)
+        // Define the exact structural sequence mandated by Payfast's documentation
+        string[] mandatorySequence =
+        [
+            "merchant_id",
+            "merchant_key",
+            "return_url",
+            "cancel_url",
+            "notify_url",
+            "name_first",
+            "name_last",
+            "email_address",
+            "cell_number",
+            "m_payment_id",
+            "amount",
+            "item_name",
+            "item_description",
+            "custom_int1",
+            "custom_int2",
+            "custom_int3",
+            "custom_int4",
+            "custom_int5",
+            "custom_str1",
+            "custom_str2",
+            "custom_str3",
+            "custom_str4",
+            "custom_str5",
+            "email_confirmation",
+            "confirmation_address",
+            "payment_method",
+            "subscription_type",
+            "billing_date",
+            "recurring_amount",
+            "frequency",
+            "cycles"
+        ];
+
+        // 1. Iterate explicitly by the mandatory positional array sequence instead of the dictionary's internal order
+        foreach (string key in mandatorySequence)
         {
-            if (string.IsNullOrEmpty(kvp.Value))
-                continue;
+            // Only append if the key exists in your source dictionary and contains data
+            if (data.TryGetValue(key, out string? rawValue) && !string.IsNullOrEmpty(rawValue))
+            {
+                // Payfast requires spaces to be '+' signs. HttpUtility does this natively.
+                string encodedVal = HttpUtility.UrlEncode(rawValue.Trim());
 
-            if (kvp.Key.Equals("signature", StringComparison.OrdinalIgnoreCase))
-                continue;
+                // Payfast requires all OTHER percent-encoded hex arrays to be UPPERCASE (e.g., %3A instead of %3a)
+                string val = Regex.Replace(encodedVal, "%[0-9A-Fa-f]{2}", m => m.Value.ToUpperInvariant());
 
-            string key = kvp.Key;
-
-            // 1. Payfast requires spaces to be '+' signs. HttpUtility does this perfectly.
-            string encodedVal = HttpUtility.UrlEncode(kvp.Value.Trim());
-
-            // 2. Payfast requires all OTHER percent-encoded hex arrays to be UPPERCASE (e.g., %3A instead of %3a)
-            string val = Regex.Replace(encodedVal, "%[0-9A-Fa-f]{2}", m => m.Value.ToUpperInvariant());
-
-            pfOutput.Append($"{key}={val}&");
+                pfOutput.Append($"{key}={val}&");
+            }
         }
 
         string getString = pfOutput.Length > 0
@@ -172,7 +205,6 @@ public sealed partial class PayfastService(IDbContextFactory<MidrandBooksDbConte
 
         if (!string.IsNullOrWhiteSpace(passPhrase))
         {
-            // Apply the exact same encoding rule to your passphrase
             string encodedPassphrase = HttpUtility.UrlEncode(passPhrase.Trim());
             string safePassphrase = Regex.Replace(encodedPassphrase, "%[0-9A-Fa-f]{2}", m => m.Value.ToUpperInvariant());