diff --git a/src/Formatter/COFormatter.php b/src/Formatter/COFormatter.php
index 3b9ee8b..6b46dce 100644
--- a/src/Formatter/COFormatter.php
+++ b/src/Formatter/COFormatter.php
@@ -13,22 +13,35 @@
  * The first 2 digits represent the department and can range from 00 to 32.
  *
  * @see https://en.wikipedia.org/wiki/List_of_postal_codes
- * @see https://en.wikipedia.org/wiki/Postal_codes_in_Colombia
+ * @see https://es.wikipedia.org/wiki/Anexo:C%C3%B3digos_postales_de_Colombia
  */
 class COFormatter implements CountryPostcodeFormatter
 {
+    protected $departments = [
+        '05', '08', '11', '13',
+        '15', '17', '18', '19',
+        '20', '23', '25', '27',
+        '41', '44', '47', '50',
+        '52', '54', '63', '66',
+        '68', '70', '73', '76',
+        '81', '85', '86', '88',
+        '91', '94', '95', '97',
+        '99'
+    ];
+
     /**
      * {@inheritdoc}
      */
     public function format(string $postcode) : ?string
     {
-        if (preg_match('/^[0-9]{6}$/', $postcode) !== 1) {
+        if (preg_match('/^\d{2}(?!0000)\d{4}$/', $postcode) !== 1) {
             return null;
         }
 
+
         $department = substr($postcode, 0, 2);
 
-        if ($department > '32') {
+        if (!in_array($department, $this->departments, true)) {
             return null;
         }
 
diff --git a/tests/Formatter/COFormatterTest.php b/tests/Formatter/COFormatterTest.php
index 69a9473..136f4dc 100644
--- a/tests/Formatter/COFormatterTest.php
+++ b/tests/Formatter/COFormatterTest.php
@@ -34,10 +34,12 @@ public function providerFormat() : array
             ['123', null],
             ['1234', null],
             ['12345', null],
-            ['000000', '000000'],
-            ['123456', '123456'],
-            ['320000', '320000'],
-            ['330000', null],
+            ['000000', null],
+            ['123456', null],
+            ['661001', '661001'],
+            ['760002', '760002'],
+            ['850000', null],
+            ['850001', '850001'],
             ['990000', null],
             ['1234567', null],