diff --git a/Models/AccountAbstract.php b/Models/AccountAbstract.php
index 989b7ca..73585f7 100644
--- a/Models/AccountAbstract.php
+++ b/Models/AccountAbstract.php
@@ -31,7 +31,7 @@ abstract class AccountAbstract
      * @var int
      * @since 1.0.0
      */
-    protected $id = 0;
+    protected int $id = 0;
 
     /**
      * Type.
@@ -39,7 +39,7 @@ abstract class AccountAbstract
      * @var int
      * @since 1.0.0
      */
-    protected $type = AccountType::IMPERSONAL;
+    protected int $type = AccountType::IMPERSONAL;
 
     /**
      * Entry list.
@@ -47,7 +47,7 @@ abstract class AccountAbstract
      * @var EntryInterface[]
      * @since 1.0.0
      */
-    protected $entries = [];
+    protected array $entries = [];
 
     /**
      * Constructor.
diff --git a/Models/Balance.php b/Models/Balance.php
index 74d4bd6..10dc5a7 100644
--- a/Models/Balance.php
+++ b/Models/Balance.php
@@ -31,7 +31,7 @@ class Balance
      * @var int
      * @since 1.0.0
      */
-    private $id = 0;
+    private int $id = 0;
 
     /**
      * Balance data.
@@ -39,7 +39,7 @@ class Balance
      * @var array
      * @since 1.0.0
      */
-    private $balance = [];
+    private array $balance = [];
 
     /**
      * Balance name.
@@ -47,7 +47,7 @@ class Balance
      * @var string
      * @since 1.0.0
      */
-    private $name = '';
+    private string $name = '';
 
     /**
      * Balance description.
@@ -55,7 +55,7 @@ class Balance
      * @var string
      * @since 1.0.0
      */
-    private $description = '';
+    private string $description = '';
 
     /**
      * Get balance id
diff --git a/Models/BatchPosting.php b/Models/BatchPosting.php
index dfae6d4..1c618bd 100644
--- a/Models/BatchPosting.php
+++ b/Models/BatchPosting.php
@@ -31,7 +31,7 @@ class BatchPosting implements \Countable
      * @var int
      * @since 1.0.0
      */
-    private $id = 0;
+    private int $id = 0;
 
     /**
      * Creator.
@@ -39,7 +39,7 @@ class BatchPosting implements \Countable
      * @var int
      * @since 1.0.0
      */
-    private $creator = 0;
+    private int $creator = 0;
 
     /**
      * Created.
@@ -47,7 +47,7 @@ class BatchPosting implements \Countable
      * @var null|\DateTime
      * @since 1.0.0
      */
-    private $created = null;
+    private ?\DateTime $created = null;
 
     /**
      * Description.
@@ -55,7 +55,7 @@ class BatchPosting implements \Countable
      * @var string
      * @since 1.0.0
      */
-    private $description = '';
+    private string $description = '';
 
     /**
      * Postings.
diff --git a/Models/CostCenter.php b/Models/CostCenter.php
index 6089455..b07d45b 100644
--- a/Models/CostCenter.php
+++ b/Models/CostCenter.php
@@ -30,7 +30,7 @@ class CostCenter
      * @var int
      * @since 1.0.0
      */
-    private $id = 0;
+    private int $id = 0;
 
     /**
      * Code.
@@ -38,7 +38,7 @@ class CostCenter
      * @var string
      * @since 1.0.0
      */
-    private $code = '';
+    private string $code = '';
 
     /**
      * Name.
@@ -46,7 +46,7 @@ class CostCenter
      * @var string
      * @since 1.0.0
      */
-    private $name = '';
+    private string $name = '';
 
     /**
      * Description.
@@ -54,7 +54,7 @@ class CostCenter
      * @var string
      * @since 1.0.0
      */
-    private $description = '';
+    private string $description = '';
 
     /**
      * Get balance id
diff --git a/Models/CostObject.php b/Models/CostObject.php
index 2947dab..0670df0 100644
--- a/Models/CostObject.php
+++ b/Models/CostObject.php
@@ -30,7 +30,7 @@ class CostObject
      * @var int
      * @since 1.0.0
      */
-    private $id = 0;
+    private int $id = 0;
 
     /**
      * Code.
@@ -38,7 +38,7 @@ class CostObject
      * @var string
      * @since 1.0.0
      */
-    private $code = '';
+    private string $code = '';
 
     /**
      * Name.
@@ -46,7 +46,7 @@ class CostObject
      * @var string
      * @since 1.0.0
      */
-    private $name = '';
+    private string $name = '';
 
     /**
      * Description.
@@ -54,7 +54,7 @@ class CostObject
      * @var string
      * @since 1.0.0
      */
-    private $description = '';
+    private string $description = '';
 
     /**
      * Get balance id
diff --git a/Models/Creditor.php b/Models/Creditor.php
index bc10f97..eb9e756 100644
--- a/Models/Creditor.php
+++ b/Models/Creditor.php
@@ -33,12 +33,12 @@ class Creditor
      * @var int
      * @since 1.0.0
      */
-    protected $id = 0;
+    protected int $id = 0;
 
     /**
      * Account.
      *
-     * @var int
+     * @var null|int|phpOMS/Account/Account
      * @since 1.0.0
      */
     protected $account = null;
diff --git a/Models/Debitor.php b/Models/Debitor.php
index 48fadd0..b2e6579 100644
--- a/Models/Debitor.php
+++ b/Models/Debitor.php
@@ -33,12 +33,12 @@ class Debitor
      * @var int
      * @since 1.0.0
      */
-    protected $id = 0;
+    protected int $id = 0;
 
     /**
      * Account.
      *
-     * @var int
+     * @var null|int|phpOMS/Account/Account
      * @since 1.0.0
      */
     protected $account = null;