diff --git a/app/Controllers/Api/v1/MedicalStoreApi.php b/app/Controllers/Api/v1/MedicalStoreApi.php
index 747438b..4f558de 100644
--- a/app/Controllers/Api/v1/MedicalStoreApi.php
+++ b/app/Controllers/Api/v1/MedicalStoreApi.php
@@ -531,20 +531,27 @@ class MedicalStoreApi extends BaseController
             }
         }
 
-        $gstRates = [0, 5, 12, 18, 28];
+        // Current GST Slabs: 0% (Nil/Exempt), 5% (Common/Basic), 18% (Standard), 40% (Demerit/Sin), plus legacy 12% and 28%
+        $gstRates = [0, 5, 18, 40, 12, 28];
         if ($this->db->tableExists('med_gst_per')) {
             $gRows = $this->db->table('med_gst_per')->select('gst_per')->orderBy('gst_per', 'ASC')->get()->getResultArray();
             if (!empty($gRows)) {
-                $customRates = [];
+                $mappedRates = [];
                 foreach ($gRows as $gr) {
-                    $r = (float)$gr['gst_per'];
-                    if (!in_array($r, $customRates, true)) {
-                        $customRates[] = $r;
+                    $half = (float)$gr['gst_per'];
+                    $tot = round($half * 2, 2); // med_gst_per stores CGST half-rate
+                    if ($tot > 0 && !in_array($tot, $mappedRates)) {
+                        $mappedRates[] = $tot;
                     }
                 }
-                if (!empty($customRates)) {
-                    $gstRates = $customRates;
+                foreach ([0, 5, 18, 40, 12, 28] as $reqRate) {
+                    if (!in_array($reqRate, $mappedRates)) {
+                        $mappedRates[] = $reqRate;
+                    }
                 }
+                $mappedRates = array_values(array_unique($mappedRates));
+                sort($mappedRates);
+                $gstRates = $mappedRates;
             }
         }
 
diff --git a/app/Controllers/Medical.php b/app/Controllers/Medical.php
index d21c581..3f494a0 100644
--- a/app/Controllers/Medical.php
+++ b/app/Controllers/Medical.php
@@ -11053,11 +11053,13 @@ class Medical extends BaseController
             $camt = (float) ($row['cgst_2_5'] ?? 0)
                 + (float) ($row['cgst_6'] ?? 0)
                 + (float) ($row['cgst_9'] ?? 0)
-                + (float) ($row['cgst_14'] ?? 0);
+                + (float) ($row['cgst_14'] ?? 0)
+                + (float) ($row['cgst_20'] ?? 0);
             $samt = (float) ($row['sgst_2_5'] ?? 0)
                 + (float) ($row['sgst_6'] ?? 0)
                 + (float) ($row['sgst_9'] ?? 0)
-                + (float) ($row['sgst_14'] ?? 0);
+                + (float) ($row['sgst_14'] ?? 0)
+                + (float) ($row['sgst_20'] ?? 0);
 
             $hsnData[] = [
                 'num' => $num++,
@@ -11240,6 +11242,9 @@ class Medical extends BaseController
             . 'ROUND(SUM(CASE WHEN ' . $cgstPerExpr . '=14 THEN ' . $taxableExpr . ' ELSE 0 END),0) AS sale_28_amount,'
             . 'SUM(CASE WHEN ' . $cgstPerExpr . '=14 THEN ' . $cgstExpr . ' ELSE 0 END) AS cgst_14,'
             . 'SUM(CASE WHEN ' . $cgstPerExpr . '=14 THEN ' . $sgstExpr . ' ELSE 0 END) AS sgst_14,'
+            . 'ROUND(SUM(CASE WHEN ' . $cgstPerExpr . '=20 THEN ' . $taxableExpr . ' ELSE 0 END),0) AS sale_40_amount,'
+            . 'SUM(CASE WHEN ' . $cgstPerExpr . '=20 THEN ' . $cgstExpr . ' ELSE 0 END) AS cgst_20,'
+            . 'SUM(CASE WHEN ' . $cgstPerExpr . '=20 THEN ' . $sgstExpr . ' ELSE 0 END) AS sgst_20,'
             . 'ROUND(SUM(CASE WHEN ' . $cgstPerExpr . '=0 THEN ' . $taxableExpr . ' ELSE 0 END),0) AS sale_0_amount '
             . 'FROM invoice_med_master m '
             . 'JOIN inv_med_item i ON m.' . $mid . '=i.' . $invMedId . ' '
diff --git a/app/Database/Migrations/2026-09-10-000004_UpdateGstSlabsAcrossMasters.php b/app/Database/Migrations/2026-09-10-000004_UpdateGstSlabsAcrossMasters.php
new file mode 100644
index 0000000..5d52de1
--- /dev/null
+++ b/app/Database/Migrations/2026-09-10-000004_UpdateGstSlabsAcrossMasters.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class UpdateGstSlabsAcrossMasters extends Migration
+{
+    public function up()
+    {
+        // 1. Ensure med_gst_per exists and contains the current GST slabs (half-rates for CGST/SGST)
+        // Slabs: 0% -> 0.00, 5% -> 2.50, 18% -> 9.00, 40% -> 20.00, 12% (legacy) -> 6.00, 28% (legacy) -> 14.00
+        if ($this->db->tableExists('med_gst_per')) {
+            $requiredRates = [
+                0.00,
+                2.50,
+                6.00,
+                9.00,
+                14.00,
+                20.00
+            ];
+
+            foreach ($requiredRates as $rate) {
+                $row = $this->db->query("SELECT id FROM `med_gst_per` WHERE ROUND(`gst_per`, 2) = ROUND(?, 2) LIMIT 1", [$rate])->getRowArray();
+
+                if (!$row) {
+                    $this->db->table('med_gst_per')->insert([
+                        'gst_per' => $rate
+                    ]);
+                }
+            }
+        }
+    }
+
+    public function down()
+    {
+        // Keep rates for safety of historical data
+    }
+}
diff --git a/app/Views/medical/product_edit.php b/app/Views/medical/product_edit.php
index fa80da1..f552512 100644
--- a/app/Views/medical/product_edit.php
+++ b/app/Views/medical/product_edit.php
@@ -121,33 +121,34 @@ $flag = static function ($v): string {
             <div class="col-md-1">
                 <label class="form-label">CGST</label>
                 <select class="form-select" name="input_CGST" id="input_CGST">
-                    <?php if (! empty($gstRates)): ?>
-                        <?php foreach ($gstRates as $rate): ?>
-                            <?php $gstValue = trim((string) ($rate->gst_per ?? '0')); ?>
-                            <?php if ($gstValue === '') { $gstValue = '0'; } ?>
-                            <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === (float) $cgst) ? 'selected' : '' ?>><?= esc($gstValue) ?></option>
-                        <?php endforeach; ?>
-                    <?php else: ?>
-                        <?php foreach (['0', '2.5', '5', '6', '9', '12'] as $gstValue): ?>
-                            <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === (float) $cgst) ? 'selected' : '' ?>><?= esc($gstValue) ?></option>
-                        <?php endforeach; ?>
-                    <?php endif; ?>
+                    <?php 
+                    $formatGstOptionLabel = static function($val) {
+                        $f = (float)$val;
+                        if ($f == 0.0) return '0% (Exempt)';
+                        if ($f == 2.5) return '2.5% (5% GST)';
+                        if ($f == 9.0) return '9.0% (18% GST)';
+                        if ($f == 20.0) return '20% (40% GST)';
+                        if ($f == 6.0) return '6.0% (12% Legacy)';
+                        if ($f == 14.0) return '14% (28% Legacy)';
+                        return $val . '%';
+                    };
+                    $standardGstValues = ['0', '2.5', '9', '20', '6', '14'];
+                    $rawRates = !empty($gstRates) ? array_map(static fn($r) => trim((string)($r->gst_per ?? '0')), $gstRates) : $standardGstValues;
+                    foreach ($standardGstValues as $sv) {
+                        if (!in_array($sv, $rawRates, true)) $rawRates[] = $sv;
+                    }
+                    ?>
+                    <?php foreach ($rawRates as $gstValue): ?>
+                        <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === (float) $cgst) ? 'selected' : '' ?>><?= esc($formatGstOptionLabel($gstValue)) ?></option>
+                    <?php endforeach; ?>
                 </select>
             </div>
             <div class="col-md-1">
                 <label class="form-label">SGST</label>
                 <select class="form-select" name="input_SGST" id="input_SGST">
-                    <?php if (! empty($gstRates)): ?>
-                        <?php foreach ($gstRates as $rate): ?>
-                            <?php $gstValue = trim((string) ($rate->gst_per ?? '0')); ?>
-                            <?php if ($gstValue === '') { $gstValue = '0'; } ?>
-                            <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === (float) $sgst) ? 'selected' : '' ?>><?= esc($gstValue) ?></option>
-                        <?php endforeach; ?>
-                    <?php else: ?>
-                        <?php foreach (['0', '2.5', '5', '6', '9', '12'] as $gstValue): ?>
-                            <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === (float) $sgst) ? 'selected' : '' ?>><?= esc($gstValue) ?></option>
-                        <?php endforeach; ?>
-                    <?php endif; ?>
+                    <?php foreach ($rawRates as $gstValue): ?>
+                        <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === (float) $sgst) ? 'selected' : '' ?>><?= esc($formatGstOptionLabel($gstValue)) ?></option>
+                    <?php endforeach; ?>
                 </select>
             </div>
 
diff --git a/app/Views/medical/purchase_invoice_edit.php b/app/Views/medical/purchase_invoice_edit.php
index 2ff987b..ddd2fb4 100644
--- a/app/Views/medical/purchase_invoice_edit.php
+++ b/app/Views/medical/purchase_invoice_edit.php
@@ -103,37 +103,34 @@
                     <div class="col-md-2">
                         <label class="form-label">CGST</label>
                         <select class="form-select form-select-sm" name="input_CGST" id="input_CGST" onchange="calculate()">
-                            <?php if (! empty($gstRates)): ?>
-                                <?php foreach ($gstRates as $rate): ?>
-                                    <?php $gstValue = (string) ($rate->gst_per ?? '0'); ?>
-                                    <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === 2.5) ? 'selected' : '' ?>><?= esc($gstValue) ?></option>
-                                <?php endforeach; ?>
-                            <?php else: ?>
-                                <option value="0">0</option>
-                                <option value="2.5" selected>2.5</option>
-                                <option value="5">5</option>
-                                <option value="6">6</option>
-                                <option value="9">9</option>
-                                <option value="12">12</option>
-                            <?php endif; ?>
+                            <?php 
+                            $formatGstLabel = static function($val) {
+                                $f = (float)$val;
+                                if ($f == 0.0) return '0% (Exempt)';
+                                if ($f == 2.5) return '2.5% (5% GST)';
+                                if ($f == 9.0) return '9.0% (18% GST)';
+                                if ($f == 20.0) return '20% (40% GST)';
+                                if ($f == 6.0) return '6.0% (12% Legacy)';
+                                if ($f == 14.0) return '14% (28% Legacy)';
+                                return $val . '%';
+                            };
+                            $stdRates = ['0', '2.5', '9', '20', '6', '14'];
+                            $pRates = !empty($gstRates) ? array_map(static fn($r) => trim((string)($r->gst_per ?? '0')), $gstRates) : $stdRates;
+                            foreach ($stdRates as $sr) {
+                                if (!in_array($sr, $pRates, true)) $pRates[] = $sr;
+                            }
+                            ?>
+                            <?php foreach ($pRates as $gstValue): ?>
+                                <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === 2.5) ? 'selected' : '' ?>><?= esc($formatGstLabel($gstValue)) ?></option>
+                            <?php endforeach; ?>
                         </select>
                     </div>
                     <div class="col-md-2">
                         <label class="form-label">SGST / IGST</label>
                         <select class="form-select form-select-sm" name="input_SGST" id="input_SGST" onchange="calculate()">
-                            <?php if (! empty($gstRates)): ?>
-                                <?php foreach ($gstRates as $rate): ?>
-                                    <?php $gstValue = (string) ($rate->gst_per ?? '0'); ?>
-                                    <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === 2.5) ? 'selected' : '' ?>><?= esc($gstValue) ?></option>
-                                <?php endforeach; ?>
-                            <?php else: ?>
-                                <option value="0">0</option>
-                                <option value="2.5" selected>2.5</option>
-                                <option value="5">5</option>
-                                <option value="6">6</option>
-                                <option value="9">9</option>
-                                <option value="12">12</option>
-                            <?php endif; ?>
+                            <?php foreach ($pRates as $gstValue): ?>
+                                <option value="<?= esc($gstValue) ?>" <?= ((float) $gstValue === 2.5) ? 'selected' : '' ?>><?= esc($formatGstLabel($gstValue)) ?></option>
+                            <?php endforeach; ?>
                         </select>
                     </div>
                     <div class="col-md-2">
diff --git a/app/Views/medical/report_gst_invoice_hsn_data.php b/app/Views/medical/report_gst_invoice_hsn_data.php
index 45ba1cb..853bd0c 100644
--- a/app/Views/medical/report_gst_invoice_hsn_data.php
+++ b/app/Views/medical/report_gst_invoice_hsn_data.php
@@ -30,6 +30,9 @@ $showHeader = !empty($showHeader);
             <th class="text-end">Tax.Amt.28%</th>
             <th class="text-end">CGST 14%</th>
             <th class="text-end">SGST 14%</th>
+            <th class="text-end">Tax.Amt.40%</th>
+            <th class="text-end">CGST 20%</th>
+            <th class="text-end">SGST 20%</th>
             <th class="text-end">Tax.Amt.0%</th>
         </tr>
         </thead>
@@ -54,6 +57,9 @@ $showHeader = !empty($showHeader);
                     <td class="text-end"><?= esc(number_format((float) ($row['sale_28_amount'] ?? 0), 2)) ?></td>
                     <td class="text-end"><?= esc(number_format((float) ($row['cgst_14'] ?? 0), 2)) ?></td>
                     <td class="text-end"><?= esc(number_format((float) ($row['sgst_14'] ?? 0), 2)) ?></td>
+                    <td class="text-end"><?= esc(number_format((float) ($row['sale_40_amount'] ?? 0), 2)) ?></td>
+                    <td class="text-end"><?= esc(number_format((float) ($row['cgst_20'] ?? 0), 2)) ?></td>
+                    <td class="text-end"><?= esc(number_format((float) ($row['sgst_20'] ?? 0), 2)) ?></td>
                     <td class="text-end"><?= esc(number_format((float) ($row['sale_0_amount'] ?? 0), 2)) ?></td>
                 </tr>
             <?php endforeach; ?>
diff --git a/app/Views/medical/report_gst_invoice_list_data.php b/app/Views/medical/report_gst_invoice_list_data.php
index 2450ca7..3292829 100644
--- a/app/Views/medical/report_gst_invoice_list_data.php
+++ b/app/Views/medical/report_gst_invoice_list_data.php
@@ -32,6 +32,9 @@ $showHeader = !empty($showHeader);
             <th class="text-end">Tax.Amt.28%</th>
             <th class="text-end">CGST 14%</th>
             <th class="text-end">SGST 14%</th>
+            <th class="text-end">Tax.Amt.40%</th>
+            <th class="text-end">CGST 20%</th>
+            <th class="text-end">SGST 20%</th>
             <th class="text-end">Tax.Amt.0%</th>
         </tr>
         </thead>
@@ -58,6 +61,9 @@ $showHeader = !empty($showHeader);
                     <td class="text-end"><?= esc(number_format((float) ($row['sale_28_amount'] ?? 0), 2)) ?></td>
                     <td class="text-end"><?= esc(number_format((float) ($row['cgst_14'] ?? 0), 2)) ?></td>
                     <td class="text-end"><?= esc(number_format((float) ($row['sgst_14'] ?? 0), 2)) ?></td>
+                    <td class="text-end"><?= esc(number_format((float) ($row['sale_40_amount'] ?? 0), 2)) ?></td>
+                    <td class="text-end"><?= esc(number_format((float) ($row['cgst_20'] ?? 0), 2)) ?></td>
+                    <td class="text-end"><?= esc(number_format((float) ($row['sgst_20'] ?? 0), 2)) ?></td>
                     <td class="text-end"><?= esc(number_format((float) ($row['sale_0_amount'] ?? 0), 2)) ?></td>
                 </tr>
             <?php endforeach; ?>
diff --git a/public/App/MedicalStore/index.html b/public/App/MedicalStore/index.html
index 8e37938..b5f1c67 100644
--- a/public/App/MedicalStore/index.html
+++ b/public/App/MedicalStore/index.html
@@ -4047,7 +4047,7 @@ function PurchaseView({ store, notify }) {
     const [isSearchingMeds, setIsSearchingMeds] = useState(false);
     const [showMasterModal, setShowMasterModal] = useState(false);
     const [masterTargetRow, setMasterTargetRow] = useState(null);
-    const [supportData, setSupportData] = useState({ formulations: [], companies: [], gst_rates: [0, 5, 12, 18, 28], schedules: [] });
+    const [supportData, setSupportData] = useState({ formulations: [], companies: [], gst_rates: [0, 5, 18, 40, 12, 28], schedules: [] });
     const [isSavingMaster, setIsSavingMaster] = useState(false);
     const [masterForm, setMasterForm] = useState({
         item_name: '',
@@ -4056,7 +4056,7 @@ function PurchaseView({ store, notify }) {
         units_per_pack: 10,
         packing: '10',
         hsn_code: '3004',
-        gst_rate: 12,
+        gst_rate: 5,
         drug_schedule: 'Schedule H',
         company_name: '',
         min_reorder_level: 10
@@ -5819,11 +5819,12 @@ function PurchaseView({ store, notify }) {
                                                             handleItemFormChange('sgst_pct', val);
                                                         }}
                                                     >
-                                                        <option value="0">0%</option>
-                                                        <option value="2.5">2.5%</option>
-                                                        <option value="6">6.0%</option>
-                                                        <option value="9">9.0%</option>
-                                                        <option value="14">14.0%</option>
+                                                        <option value="0">0% (Nil / Exempt)</option>
+                                                        <option value="2.5">2.5% (5% GST)</option>
+                                                        <option value="9">9.0% (18% GST)</option>
+                                                        <option value="20">20.0% (40% GST)</option>
+                                                        <option value="6">6.0% (12% Legacy)</option>
+                                                        <option value="14">14.0% (28% Legacy)</option>
                                                     </select>
                                                 </div>
                                                 <div className="col-md-2 col-6">
@@ -5833,11 +5834,12 @@ function PurchaseView({ store, notify }) {
                                                         value={itemForm.sgst_pct} 
                                                         onChange={(e) => handleItemFormChange('sgst_pct', parseFloat(e.target.value) || 0)}
                                                     >
-                                                        <option value="0">0%</option>
-                                                        <option value="2.5">2.5%</option>
-                                                        <option value="6">6.0%</option>
-                                                        <option value="9">9.0%</option>
-                                                        <option value="14">14.0%</option>
+                                                        <option value="0">0% (Nil / Exempt)</option>
+                                                        <option value="2.5">2.5% (5% GST)</option>
+                                                        <option value="9">9.0% (18% GST)</option>
+                                                        <option value="20">20.0% (40% GST)</option>
+                                                        <option value="6">6.0% (12% Legacy)</option>
+                                                        <option value="14">14.0% (28% Legacy)</option>
                                                     </select>
                                                 </div>
                                                 <div className="col-md-2 col-6">
@@ -7270,9 +7272,12 @@ function PurchaseView({ store, notify }) {
                                                     value={masterForm.gst_rate} 
                                                     onChange={(e) => setMasterForm({ ...masterForm, gst_rate: Number(e.target.value) })}
                                                 >
-                                                    {(supportData.gst_rates || [0, 5, 12, 18, 28]).map((g, idx) => (
-                                                        <option key={idx} value={g}>{g}% GST</option>
-                                                    ))}
+                                                    <option value="0">0% (Nil / Exempt)</option>
+                                                    <option value="5">5% (Common / Basic Services)</option>
+                                                    <option value="18">18% (Standard - Most Products)</option>
+                                                    <option value="40">40% (Demerit / Sin Tax)</option>
+                                                    <option value="12">12% (Legacy Medicine Slab)</option>
+                                                    <option value="28">28% (Legacy High Slab)</option>
                                                 </select>
                                             </div>
                                             <div className="col-md-3">
@@ -7684,11 +7689,12 @@ function PurchaseView({ store, notify }) {
                                                                             setPoCreateForm({ ...poCreateForm, items });
                                                                         }}
                                                                     >
-                                                                        <option value="0">0%</option>
+                                                                        <option value="0">0% (Exempt)</option>
                                                                         <option value="5">5%</option>
-                                                                        <option value="12">12%</option>
                                                                         <option value="18">18%</option>
-                                                                        <option value="28">28%</option>
+                                                                        <option value="40">40%</option>
+                                                                        <option value="12">12% (Legacy)</option>
+                                                                        <option value="28">28% (Legacy)</option>
                                                                     </select>
                                                                 </td>
                                                                 <td className="text-end fw-bold">