From 6ffbf6fa865470b479684441a109b1cc43c5f7ea Mon Sep 17 00:00:00 2001
From: Leo <leo@jirehgroup.asia>
Date: Tue, 15 Sep 2026 10:28:48 +0700
Subject: [PATCH] feat(tax): add Singapore GST community tax pack

---
 main/tax-packs/community-singapore.json | 55 +++++++++++++++++++++++++
 tests/community-tax-packs.test.ts       | 18 +++++++-
 2 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 main/tax-packs/community-singapore.json

diff --git a/main/tax-packs/community-singapore.json b/main/tax-packs/community-singapore.json
new file mode 100644
index 000000000..285b2249d
--- /dev/null
+++ b/main/tax-packs/community-singapore.json
@@ -0,0 +1,55 @@
+{
+  "schemaVersion": 1,
+  "id": "community-singapore",
+  "publisher": "FloCafe Community",
+  "sourceType": "community",
+  "version": "0.0.1",
+  "country": "SG",
+  "jurisdiction": "*",
+  "currency": "SGD",
+  "effectiveFrom": "2026-01-01",
+  "publishedAt": "2026-08-24",
+  "minFloVersion": "2.4.0",
+  "taxPoint": "finalized_at",
+  "inclusivePricingDefault": false,
+  "registrationNumberLabel": "UEN",
+  "registrationNumberFormat": {
+    "pattern": "^(?:\\d{8,9}[A-Z]|[ST]\\d{2}[A-Z]{2}\\d{4}[A-Z])$",
+    "description": "Singapore UEN (e.g. 12345678A, 200812345A, or T08LL1234A)"
+  },
+  "categories": [
+    { "id": "standard", "label": "Standard (GST 9%)", "ruleIds": ["gst"] },
+    { "id": "packaging", "label": "Packaging", "ruleIds": ["gst"] },
+    { "id": "delivery", "label": "Delivery", "ruleIds": ["gst"] },
+    { "id": "service_charge", "label": "Service charge", "ruleIds": ["gst"] },
+    { "id": "addon", "label": "Add-on", "ruleIds": ["gst"] },
+    { "id": "unclassified", "label": "Unclassified", "ruleIds": ["gst"] }
+  ],
+  "defaultCategories": {
+    "product": "standard",
+    "packaging": "packaging",
+    "delivery": "delivery",
+    "service_charge": "service_charge",
+    "addon": "addon"
+  },
+  "unclassifiedCategoryId": "unclassified",
+  "rules": [
+    {
+      "id": "gst",
+      "label": "GST",
+      "type": "percent",
+      "categoryIds": ["standard", "packaging", "delivery", "service_charge", "addon", "unclassified"],
+      "rate": "9"
+    }
+  ],
+  "taxRounding": {
+    "scope": "document",
+    "method": "half_up",
+    "decimalPlaces": 2,
+    "remainderAllocation": "largest_remainder"
+  },
+  "payableRounding": {
+    "increment": "0.01",
+    "method": "half_up"
+  }
+}
diff --git a/tests/community-tax-packs.test.ts b/tests/community-tax-packs.test.ts
index d34638924..9e49fb19d 100644
--- a/tests/community-tax-packs.test.ts
+++ b/tests/community-tax-packs.test.ts
@@ -56,7 +56,7 @@ function main() {
   }
 
   const packs = loadCommunityPacks();
-  assert.ok(packs.length >= 13, `expected at least 13 community packs, found ${packs.length}`);
+  assert.ok(packs.length >= 14, `expected at least 14 community packs, found ${packs.length}`);
 
   try {
     for (const { file, pack } of packs) {
@@ -128,6 +128,22 @@ function main() {
           `${file}/${category.id}: payable total must be finite and non-negative`);
       }
       console.log(`  ✓ every category produces a sane, non-negative calculation`);
+
+      if (pack.country === 'SG' && pack.registrationNumberFormat?.pattern) {
+        const regex = new RegExp(pack.registrationNumberFormat.pattern, 'i');
+        assert.ok(regex.test('12345678A'), `${file}: must accept 8-digit business UEN`);
+        assert.ok(regex.test('52812345X'), `${file}: must accept 8-digit business UEN`);
+        assert.ok(regex.test('200812345A'), `${file}: must accept 9-digit company UEN`);
+        assert.ok(regex.test('199912345Z'), `${file}: must accept 9-digit company UEN`);
+        assert.ok(regex.test('T08LL1234A'), `${file}: must accept LLP UEN`);
+        assert.ok(regex.test('S85FC1234B'), `${file}: must accept foreign company UEN`);
+        assert.ok(regex.test('T20SS0001D'), `${file}: must accept society UEN`);
+        assert.equal(regex.test('1234567A'), false, `${file}: must reject 7-digit UEN`);
+        assert.equal(regex.test('1234567890A'), false, `${file}: must reject 10-digit numeric UEN`);
+        assert.equal(regex.test('R08LL1234A'), false, `${file}: must reject R prefix`);
+        assert.equal(regex.test('T08123456A'), false, `${file}: must reject missing entity type letters`);
+        console.log(`  ✓ registrationNumberFormat validates Singapore UEN test vectors`);
+      }
     }
   } finally {
     closeDatabase();