diff --git a/Models/IncomeStatement.php b/Models/IncomeStatement.php
index f11e233..b8e9d2f 100755
--- a/Models/IncomeStatement.php
+++ b/Models/IncomeStatement.php
@@ -32,7 +32,19 @@ class IncomeStatement
      */
     protected int $id = 0;
 
+    /**
+     * Date.
+     *
+     * @var null|\DateTime
+     * @since 1.0.0
+     */
     private ?\DateTime $date = null;
 
+    /**
+     * Income statement structure.
+     *
+     * @var array
+     * @since 1.0.0
+     */
     private array $incomeStatement = [];
 }
diff --git a/Models/TimeRangeType.php b/Models/TimeRangeType.php
index 309de72..8167731 100755
--- a/Models/TimeRangeType.php
+++ b/Models/TimeRangeType.php
@@ -33,4 +33,8 @@ abstract class TimeRangeType extends Enum
     public const RECEIPT_DATE = 2; /* Date of the receipt */
 
     public const ASSOCIATED_DATE = 3; /* Date of the association (e.g. when did the articles arrive) */
+
+    public const PERIOD_DATE = 4; /* Date of the period this booking is assoziated with */
+
+    public const SQUARED_DATE = 5; /* Date of when the entry got squared/balanced */
 }