diff --git a/coretabs.user.js b/coretabs.user.js
index c05e3b0..73e833b 100644
--- a/coretabs.user.js
+++ b/coretabs.user.js
@@ -799,7 +799,8 @@
       if (response.ok) {
         const data = await response.json();
         const reference = data?.Payload?.[0]?.Reference;
-        if (reference) return reference; // Success on primary API
+        const taxperiod = data?.Payload?.[0]?.TaxPeriod;
+        if (reference && taxperiod) return {reference, taxperiod}; // Success on primary API
       }
     } catch (error) {
       console.warn("Primary API for C02Form failed, trying fallback.", error);
@@ -821,7 +822,8 @@
     }
     const fallbackData = await fallbackResponse.json();
     const fallbackReference = fallbackData?.Payload?.Details?.[0]?.Reference;
-    if (fallbackReference) return fallbackReference; // Success on fallback API
+    const fallbackTaxPeriod = fallbackData?.Payload?.Details?.[0]?.TaxPeriod;
+    if (fallbackReference && fallbackTaxPeriod) return {reference: fallbackReference, taxperiod: fallbackTaxPeriod}; // Success on fallback API
 
     // 3. If both fail
     throw new Error(
@@ -829,7 +831,7 @@
     );
   }
 
-  async function fetchRefundReview(caseId, refNumber) {
+  async function fetchRefundReview(caseId, refNumber, taxPeriod) {
     const responseArea = document.querySelector(
       "#tab-refund .results-container",
     );
@@ -842,6 +844,7 @@
           TaxPaymentCode: "100",
           TaxReturnType: "VAT_VATR",
           ReferenceNumber: refNumber,
+          TaxPeriod: taxPeriod,
         },
         fetchOptions = {
           method: "POST",