diff --git a/src/Enums/FeesPercentCategory.php b/src/Enums/FeesPercentCategory.php
index 4c91fca..e9a5afc 100644
--- a/src/Enums/FeesPercentCategory.php
+++ b/src/Enums/FeesPercentCategory.php
@@ -73,7 +73,7 @@ enum FeesPercentCategory: int
 
     
     /**
-     *  ΤΕισφορά δακοκτονίας [ποσό]
+     *  Εισφορά δακοκτονίας [ποσό]
      */
     case TYPE_12 = 12;
     
diff --git a/src/Services/CategoryClassificationCollection.php b/src/Services/CategoryClassificationCollection.php
index dec0b36..91c3bca 100644
--- a/src/Services/CategoryClassificationCollection.php
+++ b/src/Services/CategoryClassificationCollection.php
@@ -108,7 +108,7 @@ public function getIterator(): Traversable
 
     public function isEmpty(): bool
     {
-        return empty($this->toArray());
+        return empty($this->classifications);
     }
 
     private function toEnum(mixed $value): IncomeClassificationCategory|ExpenseClassificationCategory|null
diff --git a/src/Services/TypeClassificationCollection.php b/src/Services/TypeClassificationCollection.php
index c477e37..608ff8a 100644
--- a/src/Services/TypeClassificationCollection.php
+++ b/src/Services/TypeClassificationCollection.php
@@ -12,15 +12,27 @@
 
 class TypeClassificationCollection implements ArrayAccess, IteratorAggregate
 {
+    /**
+     * @var array<int|string, IncomeClassificationType|ExpenseClassificationType|string> $classifications
+     */
     private array $classifications;
     private bool  $isIncome;
 
+    /**
+     * @param  array<int|string, IncomeClassificationType|ExpenseClassificationType|string>  $classifications
+     * @param  bool  $isIncome
+     */
     public function __construct(array $classifications, bool $isIncome)
     {
         $this->classifications = $classifications;
         $this->isIncome = $isIncome;
     }
 
+    /**
+     * Converts classifications to an associative array with keys and labels.
+     *
+     * @return array<string, string>
+     */
     public function toKeyLabel(): array
     {
         $results = [];
@@ -34,64 +46,127 @@ public function toKeyLabel(): array
         return $results;
     }
 
+    /**
+     * Returns the keys of the classifications array.
+     *
+     * @return array<int|string>
+     */
     public function keys(): array
     {
-        return $this->toArray();
+        return $this->classifications;
     }
 
+    /**
+     * Returns the classifications as an array.
+     *
+     * @return array<int|string, IncomeClassificationType|ExpenseClassificationType|string>
+     */
     public function toArray(): array
     {
         return $this->classifications;
     }
 
+    /**
+     * Checks if an offset exists in the classifications array.
+     *
+     * @param  mixed  $offset
+     * @return bool
+     */
     public function offsetExists(mixed $offset): bool
     {
         return isset($this->classifications[$offset]);
     }
 
-    public function offsetGet(mixed $offset): mixed
+    /**
+     * Gets the value at the given offset.
+     *
+     * @param  mixed  $offset
+     * @return string|IncomeClassificationType|ExpenseClassificationType|null
+     */
+    public function offsetGet(mixed $offset): string|null|IncomeClassificationType|ExpenseClassificationType
     {
-        return $this->classifications[$offset];
+        return $this->classifications[$offset] ?? null;
     }
 
+    /**
+     * Checks if the classifications array contains a specific value.
+     *
+     * @param  mixed  $value
+     * @return bool
+     */
     public function contains(mixed $value): bool
     {
         if ($value === null) {
-            return empty($this->toArray()) || in_array($value, $this->toArray(), true);
+            return empty($this->classifications) || in_array($value, $this->classifications, true);
         }
-        
+
         if ($value instanceof BackedEnum) {
             $value = $value->value;
         }
-        
-        return in_array($value, $this->toArray(), true);
+
+        return in_array($value, $this->classifications, true);
     }
 
+    /**
+     * Gets the classification as an enum if possible.
+     *
+     * @param  mixed  $offset
+     * @return IncomeClassificationType|ExpenseClassificationType|null
+     */
     public function get(mixed $offset): IncomeClassificationType|ExpenseClassificationType|null
     {
         return $this->toEnum($offset);
     }
 
+    /**
+     * Sets the value at the given offset.
+     *
+     * @param  mixed  $offset
+     * @param  IncomeClassificationType|ExpenseClassificationType|string  $value
+     * @return void
+     */
     public function offsetSet(mixed $offset, mixed $value): void
     {
         $this->classifications[$offset] = $value;
     }
 
+    /**
+     * Unsets the value at the given offset.
+     *
+     * @param  mixed  $offset
+     * @return void
+     */
     public function offsetUnset(mixed $offset): void
     {
         unset($this->classifications[$offset]);
     }
 
+    /**
+     * Returns an iterator for the classifications array.
+     *
+     * @return Traversable<int|string, IncomeClassificationType|ExpenseClassificationType|string>
+     */
     public function getIterator(): Traversable
     {
         return new ArrayIterator($this->classifications);
     }
 
+    /**
+     * Checks if the classifications array is empty.
+     *
+     * @return bool
+     */
     public function isEmpty(): bool
     {
-        return empty($this->toArray());
+        return empty($this->classifications);
     }
-    
+
+    /**
+     * Converts a value to the appropriate enum type if possible.
+     *
+     * @param  mixed  $value
+     * @return IncomeClassificationType|ExpenseClassificationType|null
+     */
     private function toEnum(mixed $value): IncomeClassificationType|ExpenseClassificationType|null
     {
         if ($value === null) {
@@ -106,4 +181,4 @@ private function toEnum(mixed $value): IncomeClassificationType|ExpenseClassific
             ? IncomeClassificationType::tryFrom($value)
             : ExpenseClassificationType::tryFrom($value);
     }
-}
\ No newline at end of file
+}
diff --git a/src/Traits/HasIterator.php b/src/Traits/HasIterator.php
index a906a05..27b8aab 100644
--- a/src/Traits/HasIterator.php
+++ b/src/Traits/HasIterator.php
@@ -2,42 +2,80 @@
 
 namespace Firebed\AadeMyData\Traits;
 
+use ArrayAccess;
 use ArrayIterator;
+use IteratorAggregate;
 use Traversable;
 
 /**
+ * Trait HasIterator
+ * 
  * @template Model
+ * @implements ArrayAccess<int|string, Model>
+ * @implements IteratorAggregate<int|string, Model>
  */
 trait HasIterator
 {
+    /**
+     * Returns an iterator for the attributes.
+     *
+     * @return Traversable<int|string, Model>
+     */
     public function getIterator(): Traversable
     {
         return new ArrayIterator($this->attributes);
     }
     
+    /**
+     * Returns the count of attributes.
+     *
+     * @return int
+     */
     public function count(): int
     {
         return count($this->attributes);
     }
     
+    /**
+     * Checks if the given offset exists in the attributes.
+     *
+     * @param int|string $offset
+     * @return bool
+     */
     public function offsetExists(mixed $offset): bool
     {
         return array_key_exists($offset, $this->attributes);
     }
 
     /**
-     * @return Model
+     * Gets the value at the given offset.
+     *
+     * @param int|string $offset
+     * @return Model|null
      */
     public function offsetGet(mixed $offset): mixed
     {
         return $this->get($offset);
     }
 
+    /**
+     * Sets the value at the given offset.
+     *
+     * @param int|string $offset
+     * @param Model $value
+     * @return void
+     */
     public function offsetSet(mixed $offset, mixed $value): void
     {
         $this->set($offset, $value);
     }
 
+    /**
+     * Unsets the value at the given offset.
+     *
+     * @param int|string $offset
+     * @return void
+     */
     public function offsetUnset(mixed $offset): void
     {
         unset($this->attributes[$offset]);