diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..9462cac
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+composer.lock
+/vendor/
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..06d6541
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,5 @@
+# Change Log
+
+## [1.0.0] - 2023-10-25
+
+ - Initial release
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4492db2
--- /dev/null
+++ b/README.md
@@ -0,0 +1,15 @@
+# e-Boekhouden.nl Api Client
+
+## Installing
+
+```bash
+composer require onetoweb/eboekhouden
+```
+
+## Usage
+
+See [Documentation](docs/index.rst)
+
+## Change Log
+
+See [Change Log](CHANGELOG.md)
\ No newline at end of file
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..68c0153
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,31 @@
+{
+    "name": "onetoweb/eboekhouden",
+    "description": "e-Boekhouden.nl API Client",
+    "keywords": [
+        "api",
+        "php",
+        "e-boekhouden.nl",
+        "e-boekhouden"
+    ],
+    "type": "library",
+    "homepage": "https://github.com/onetoweb/eboekhouden",
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "Jonathan van 't Ende",
+            "email": "jvantende@onetoweb.nl"
+        }
+    ],
+    "require": {
+        "php": ">=7.1.0",
+        "symfony/polyfill-php81": "^1.28"
+    },
+    "require-dev": {
+        "symfony/error-handler": "^5.1"
+    },
+    "autoload": {
+        "psr-4": {
+            "Onetoweb\\Eboekhouden\\": "src/"
+        }
+    }
+}
diff --git a/docs/administration.rst b/docs/administration.rst
new file mode 100644
index 0000000..275ce1e
--- /dev/null
+++ b/docs/administration.rst
@@ -0,0 +1,22 @@
+.. _top:
+.. title:: Administration
+
+`Back to index <index.rst>`_
+
+==============
+Administration
+==============
+
+.. contents::
+    :local:
+
+
+List Administrations
+````````````````````
+
+.. code-block:: php
+    
+    $result = $client->administration->list();
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/docs/article.rst b/docs/article.rst
new file mode 100644
index 0000000..6bfbae4
--- /dev/null
+++ b/docs/article.rst
@@ -0,0 +1,28 @@
+.. _top:
+.. title:: Articles
+
+`Back to index <index.rst>`_
+
+========
+Articles
+========
+
+.. contents::
+    :local:
+
+
+List Articles
+`````````````
+
+.. code-block:: php
+    
+    $result = $client->article->list([
+        'ArtikelID' => '',
+        'ArtikelOmschrijving' => '',
+        'ArtikelCode' => '',
+        'GroepOmschrijving' => '',
+        'GroepCode' => ''
+    ]);
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/docs/balance.rst b/docs/balance.rst
new file mode 100644
index 0000000..1e54db6
--- /dev/null
+++ b/docs/balance.rst
@@ -0,0 +1,40 @@
+.. _top:
+.. title:: Balance
+
+`Back to index <index.rst>`_
+
+=======
+Balance
+=======
+
+.. contents::
+    :local:
+
+
+List Balance
+````````````
+
+.. code-block:: php
+    
+    $result = $client->balance->list([
+        'KostenPlaatsId' => 0,
+        'DatumVan' => '2022-01-01',
+        'DatumTot' => '2023-12-31',
+        'Categorie' => 'DEB'
+    ]);
+
+
+Get Balance
+```````````
+
+.. code-block:: php
+    
+    $result = $client->balance->get([
+        'KostenPlaatsId' => 0,
+        'DatumVan' => '2022-01-01',
+        'DatumTot' => '2023-12-31',
+        'GbCode' => '12000'
+    ]);
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/docs/cost_center.rst b/docs/cost_center.rst
new file mode 100644
index 0000000..5997e51
--- /dev/null
+++ b/docs/cost_center.rst
@@ -0,0 +1,26 @@
+.. _top:
+.. title:: Cost Centers
+
+`Back to index <index.rst>`_
+
+============
+Cost Centers
+============
+
+.. contents::
+    :local:
+
+
+List Cost Centers
+`````````````````
+
+.. code-block:: php
+    
+    $result = $client->costCenter->list([
+        'KostenplaatsID' => '',
+        'KostenplaatsParentID' => '',
+        'Omschrijving' => ''
+    ]);
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/docs/general_ledger.rst b/docs/general_ledger.rst
new file mode 100644
index 0000000..df71cdd
--- /dev/null
+++ b/docs/general_ledger.rst
@@ -0,0 +1,54 @@
+.. _top:
+.. title:: General Ledger
+
+`Back to index <index.rst>`_
+
+==============
+General Ledger
+==============
+
+.. contents::
+    :local:
+
+
+List General Ledger Accounts
+````````````````````````````
+
+.. code-block:: php
+    
+    $result = $client->generalLedger->list([
+        'ID' => '',
+        'Code' => '',
+        'Categorie' => ''
+    ]);
+
+
+Create General Ledger Account
+`````````````````````````````
+
+.. code-block:: php
+    
+    $result = $client->generalLedger->create([
+        'ID' => '',
+        'Code' => '800001',
+        'Omschrijving' => 'Foo Bar 1',
+        'Categorie' => 'BAL',
+        'Groep' => ''
+    ]);
+
+
+Update General Ledger Account
+`````````````````````````````
+
+.. code-block:: php
+    
+    $result = $client->generalLedger->update([
+        'ID' => '10000000',
+        'Code' => '800002',
+        'Omschrijving' => 'Foo Bar 2',
+        'Categorie' => 'BAL',
+        'Groep' => ''
+    ]);
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/docs/index.rst b/docs/index.rst
new file mode 100644
index 0000000..15a8640
--- /dev/null
+++ b/docs/index.rst
@@ -0,0 +1,36 @@
+.. title:: Index
+
+===========
+Basic Usage
+===========
+
+Setup Client
+
+.. code-block:: php
+    
+    require 'vendor/autoload.php';
+    
+    use Onetoweb\Eboekhouden\Client;
+    
+    // param
+    $username = '{username}';
+    $securityCode1 = '{security_code_1}';
+    $securityCode2 = '{security_code_2}';
+    
+    // setup client
+    $client = new Client($username, $securityCode1, $securityCode2);
+
+
+========
+Examples
+========
+
+* `Administration <administration.rst>`_
+* `Balance <balance.rst>`_
+* `Invoices <invoice.rst>`_
+* `Mutations <mutation.rst>`_
+* `General Ledger <general_ledger.rst>`_
+* `Relations <relations.rst>`_
+* `Open Posts <open_post.rst>`_
+* `Cost Centers <cost_center.rst>`_
+* `Articles <article.rst>`_
diff --git a/docs/invoice.rst b/docs/invoice.rst
new file mode 100644
index 0000000..5cefa01
--- /dev/null
+++ b/docs/invoice.rst
@@ -0,0 +1,82 @@
+.. _top:
+.. title:: Invoice
+
+`Back to index <index.rst>`_
+
+=======
+Invoice
+=======
+
+.. contents::
+    :local:
+
+
+List Invoices
+`````````````
+
+.. code-block:: php
+    
+    $result = $client->invoice->list([
+        'Factuurnummer' => 'F00001',
+        'Relatiecode' => 'REL',
+        'DatumVan' => '2022-01-01',
+        'DatumTm' => '2023-12-31'
+    ]);
+
+
+Create Invoice
+``````````````
+
+.. code-block:: php
+    
+    $result = $client->invoice->create([
+        'Factuurnummer' => '',
+        'Relatiecode' => 'BV42',
+        'Datum' => '2023-10-26',
+        'Betalingstermijn' => 14,
+        'Factuursjabloon' => '',
+        'PerEmailVerzenden' => true,
+        'EmailOnderwerp' => '',
+        'EmailBericht' => '',
+        'EmailVanAdres' => '',
+        'EmailVanNaam' => '',
+        'AutomatischeIncasso' => true,
+        'IncassoIBAN' => '',
+        'IncassoMachtigingSoort' => '',
+        'IncassoMachtigingID' => '',
+        'IncassoMachtigingDatumOndertekening' => '2023-10-26',
+        'IncassoMachtigingFirst' => true,
+        'IncassoRekeningNummer' => '',
+        'IncassoTnv' => '',
+        'IncassoPlaats' => '',
+        'IncassoOmschrijvingRegel1' => '',
+        'IncassoOmschrijvingRegel2' => '',
+        'IncassoOmschrijvingRegel3' => '',
+        'InBoekhoudingPlaatsen' => true,
+        'Regels' => [
+            'cFactuurRegel' => [
+                [
+                    'Aantal' => 1.0,
+                    'Eenheid' => '',
+                    'Code' => '',
+                    'Omschrijving' => '',
+                    'PrijsPerEenheid' => 0.0,
+                    'BTWCode' => '',
+                    'TegenrekeningCode' => '',
+                    'KostenplaatsID' => 0
+                ], [
+                    'Aantal' => 1.0,
+                    'Eenheid' => '',
+                    'Code' => '',
+                    'Omschrijving' => '',
+                    'PrijsPerEenheid' => 0.0,
+                    'BTWCode' => '',
+                    'TegenrekeningCode' => '',
+                    'KostenplaatsID' => 0
+                ]
+            ]
+        ],
+    ]);
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/docs/mutation.rst b/docs/mutation.rst
new file mode 100644
index 0000000..695dabd
--- /dev/null
+++ b/docs/mutation.rst
@@ -0,0 +1,49 @@
+.. _top:
+.. title:: Mutations
+
+`Back to index <index.rst>`_
+
+=========
+Mutations
+=========
+
+.. contents::
+    :local:
+
+
+List Mutations
+``````````````
+
+.. code-block:: php
+    
+    $result = $client->mutation->list([
+        'MutatieNr' => '',
+        'MutatieNrVan' => '',
+        'MutatieNrTm' => '',
+        'Factuurnummer' => '',
+        'DatumVan' => '2022-01-01',
+        'DatumTm' => '2023-12-31'
+    ]);
+
+
+Create Mutation
+```````````````
+
+.. code-block:: php
+    
+    $result = $client->mutation->create([
+        'MutatieNr' => '',
+        'Soort' => 'Memoriaal',
+        'Datum' => '2023-10-26',
+        'Rekening' => '',
+        'RelatieCode' => '',
+        'Factuurnummer' => '',
+        'Boekstuk' => '',
+        'Omschrijving' => 'Mutatie',
+        'Betalingstermijn' => '',
+        'Betalingskenmerk' => '',
+        'InExBTW' => 'IN'
+    ]);
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/docs/open_post.rst b/docs/open_post.rst
new file mode 100644
index 0000000..442e43a
--- /dev/null
+++ b/docs/open_post.rst
@@ -0,0 +1,23 @@
+.. _top:
+.. title:: Open Posts
+
+`Back to index <index.rst>`_
+
+==========
+Open Posts
+==========
+
+.. contents::
+    :local:
+
+
+List Open Posts
+```````````````
+
+.. code-block:: php
+    
+    $type = 'Debiteuren'; // or Crediteuren
+    $result = $client->openPost->list($type);
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/docs/relations.rst b/docs/relations.rst
new file mode 100644
index 0000000..fa83165
--- /dev/null
+++ b/docs/relations.rst
@@ -0,0 +1,128 @@
+.. _top:
+.. title:: Relations
+
+`Back to index <index.rst>`_
+
+=========
+Relations
+=========
+
+.. contents::
+    :local:
+
+
+List Relations
+``````````````
+
+.. code-block:: php
+    
+    $result = $client->relation->list([
+        'Trefwoord' => '',
+        'Code' => '',
+        'ID' => ''
+    ]);
+
+
+Create Relation
+```````````````
+
+.. code-block:: php
+    
+    $result = $client->relation->create([
+        'ID' => '',
+        'AddDatum' => '2023-10-26',
+        'Code' => 'BV42',
+        'Bedrijf' => 'Bedrijf B.V.',
+        'Contactpersoon' => '',
+        'Geslacht' => '',
+        'Adres' => '',
+        'Postcode' => '',
+        'Plaats' => '',
+        'Land' => '',
+        'Adres2' => '',
+        'Postcode2' => '',
+        'Plaats2' => '',
+        'Land2' => '',
+        'Telefoon' => '',
+        'GSM' => '',
+        'FAX' => '',
+        'Email' => '',
+        'Site' => '',
+        'Notitie' => '',
+        'Bankrekening' => '',
+        'Girorekening' => '',
+        'BTWNummer' => '',
+        'KvkNummer' => '',
+        'Aanhef' => '',
+        'IBAN' => '',
+        'BIC' => '',
+        'BP' => '',
+        'Def1' => '',
+        'Def2' => '',
+        'Def3' => '',
+        'Def4' => '',
+        'Def5' => '',
+        'Def6' => '',
+        'Def7' => '',
+        'Def8' => '',
+        'Def9' => '',
+        'Def10' => '',
+        'LA' => '',
+        'Gb_ID' => '',
+        'GeenEmail' => '',
+        'NieuwsbriefgroepenCount' => ''
+    ]);
+
+
+Update Relation
+```````````````
+
+.. code-block:: php
+    
+    $result = $client->relation->update([
+        'ID' => '10000000',
+        'AddDatum' => '2023-10-26',
+        'Code' => 'BV42',
+        'Bedrijf' => 'Bedrijf B.V.',
+        'Contactpersoon' => '',
+        'Geslacht' => '',
+        'Adres' => '',
+        'Postcode' => '',
+        'Plaats' => '',
+        'Land' => '',
+        'Adres2' => '',
+        'Postcode2' => '',
+        'Plaats2' => '',
+        'Land2' => '',
+        'Telefoon' => '',
+        'GSM' => '',
+        'FAX' => '',
+        'Email' => '',
+        'Site' => '',
+        'Notitie' => '',
+        'Bankrekening' => '',
+        'Girorekening' => '',
+        'BTWNummer' => '',
+        'KvkNummer' => '',
+        'Aanhef' => '',
+        'IBAN' => '',
+        'BIC' => '',
+        'BP' => '',
+        'Def1' => '',
+        'Def2' => '',
+        'Def3' => '',
+        'Def4' => '',
+        'Def5' => '',
+        'Def6' => '',
+        'Def7' => '',
+        'Def8' => '',
+        'Def9' => '',
+        'Def10' => '',
+        'LA' => '',
+        'Gb_ID' => '',
+        'GeenEmail' => '',
+        'NieuwsbriefgroepenCount' => ''
+    ]);
+
+
+`Back to top <#top>`_
\ No newline at end of file
diff --git a/src/Client.php b/src/Client.php
new file mode 100644
index 0000000..d0414d3
--- /dev/null
+++ b/src/Client.php
@@ -0,0 +1,132 @@
+<?php
+
+namespace Onetoweb\Eboekhouden;
+
+use Onetoweb\Eboekhouden\Endpoint\Endpoints;
+use SoapClient;
+
+/**
+ * E-Boekhouden Api Client.
+ */
+class Client
+{
+    /**
+     * Get Base Wdsl
+     */
+    public const BASE_WDSL = 'https://soap.e-boekhouden.nl/soap.asmx?wsdl';
+    
+    /**
+     * @var string
+     */
+    private $username;
+    
+    /**
+     * @var string
+     */
+    private $securityCode1;
+    
+    /**
+     * @var string
+     */
+    private $securityCode2;
+    
+    /**
+     * @var string
+     */
+    private $sessionId;
+    
+    /**
+     * @var SoapClient
+     */
+    private $soapClient;
+    
+    /**
+     * @param string $username
+     * @param string $securityCode1
+     * @param string $securityCode2
+     */
+    public function __construct(string $username, string $securityCode1, string $securityCode2)
+    {
+        $this->username = $username;
+        $this->securityCode1 = $securityCode1;
+        $this->securityCode2 = $securityCode2;
+        
+        // setup soap client
+        $this->soapClient = new SoapClient(Client::BASE_WDSL, ['trace' => true]);
+        
+        // load endpoints
+        $this->loadEndpoints();
+    }
+    
+    /**
+     * @return void
+     */
+    private function loadEndpoints(): void
+    {
+        foreach (Endpoints::list() as $name => $class) {
+            $this->{$name} = new $class($this->soapClient, $this->getSessionId(), $this->securityCode2);
+        }
+    }
+    
+    /**
+     * @return SoapClient
+     */
+    public function getSoapClient(): SoapClient
+    {
+        return $this->soapClient;
+    }
+    
+    /**
+     * @return sting
+     */
+    public function getSessionId(): string
+    {
+        if ($this->sessionId === null) {
+            $this->openSession();
+        }
+        
+        return $this->sessionId;
+    }
+    
+    /**
+     * @return void
+     */
+    private function openSession(): void
+    {
+        // open session
+        $params = [
+            'Username' => $this->username,
+            'SecurityCode1' => $this->securityCode1,
+            'SecurityCode2' => $this->securityCode2
+        ];
+        $response = $this->soapClient->__soapCall('OpenSession', [$params]);
+        
+        // get session id
+        $this->sessionId = $response->OpenSessionResult->SessionID;
+    }
+    
+    /**
+     * @return void
+     */
+    private function closeSession(): void
+    {
+        // open session
+        $params = [
+            'SessionID' => $this->sessionId,
+        ];
+        $response = $this->soapClient->__soapCall('CloseSession', [$params]);
+        
+        // clear session id
+        $this->sessionId = null;
+    }
+    
+    /**
+     * Destructor.
+     */
+    public function __destruct()
+    {
+        if ($this->sessionId !== null) {
+            $this->closeSession();
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/AbstractEndpoint.php b/src/Endpoint/AbstractEndpoint.php
new file mode 100644
index 0000000..3bc413e
--- /dev/null
+++ b/src/Endpoint/AbstractEndpoint.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint;
+
+use SoapClient;
+
+/**
+ * Abstract Endpoint.
+ */
+class AbstractEndpoint implements EndpointInterface
+{
+    /**
+     * @var SoapClient
+     */
+    protected $soapClient;
+    
+    /**
+     * @var string
+     */
+    protected $sessionId;
+    
+    /**
+     * @var string
+     */
+    protected $securityCode2;
+    
+    /**
+     * @param SoapClient $soapClient
+     * @param string $sessionId
+     * @param string $securityCode2
+     */
+    public function __construct(SoapClient $soapClient, string $sessionId, string $securityCode2)
+    {
+        $this->soapClient = $soapClient;
+        $this->sessionId = $sessionId;
+        $this->securityCode2 = $securityCode2;
+    }
+    
+    /**
+     * @param mixed $response
+     * 
+     * @return array|null
+     */
+    protected function proccessResponse($response): ?array
+    {
+        return json_decode(json_encode($response), true);
+    }
+    
+    /**
+     * @param mixed $response
+     *
+     * @return array|null
+     */
+    protected function returnList(array $data): ?array
+    {
+        return array_is_list($data) ? $data : [$data];
+    }
+    
+    /**
+     * @return array $param = []
+     */
+    protected function addSession(array $param = [])
+    {
+        return array_merge([
+            'SessionID' => $this->sessionId,
+            'SecurityCode2' => $this->securityCode2,
+        ], $param);
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/EndpointInterface.php b/src/Endpoint/EndpointInterface.php
new file mode 100644
index 0000000..f5fd1fb
--- /dev/null
+++ b/src/Endpoint/EndpointInterface.php
@@ -0,0 +1,5 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint;
+
+interface EndpointInterface { }
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints.php b/src/Endpoint/Endpoints.php
new file mode 100644
index 0000000..9e0de40
--- /dev/null
+++ b/src/Endpoint/Endpoints.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint;
+
+use Onetoweb\Eboekhouden\Client;
+
+/**
+ * Endpoints.
+ */
+final class Endpoints
+{
+    /**
+     * @return array
+     */
+    public static function list(): array
+    {
+        $endpoints = [];
+        
+        $dir = __DIR__ . '/Endpoints/';
+        
+        foreach (scandir($dir) as $filename) {
+            
+            $path = $dir.$filename;
+            
+            if (is_file($path) and !in_array($filename, ['.', '..'])) {
+                
+                $endpoint = pathinfo($filename, PATHINFO_FILENAME);
+                
+                $class = __NAMESPACE__ . "\\Endpoints\\$endpoint";
+                
+                if (class_exists($class) and in_array(EndpointInterface::class, class_implements($class))) {
+                    $endpoints[lcfirst($endpoint)] = $class;
+                }
+            }
+        }
+        
+        return $endpoints;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/Administration.php b/src/Endpoint/Endpoints/Administration.php
new file mode 100644
index 0000000..6592a07
--- /dev/null
+++ b/src/Endpoint/Endpoints/Administration.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * Administration Endpoint.
+ */
+class Administration extends AbstractEndpoint
+{
+    /**
+     * @return array|null
+     */
+    public function list(): ?array
+    {
+        $params = $this->addSession();
+        
+        $response = $this->soapClient->__soapCall('GetAdministraties', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetAdministratiesResult']['Administraties']['cAdministratie'])) {
+            return $processedResponse['GetAdministratiesResult']['Administraties']['cAdministratie'];
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/Article.php b/src/Endpoint/Endpoints/Article.php
new file mode 100644
index 0000000..8e2ea35
--- /dev/null
+++ b/src/Endpoint/Endpoints/Article.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * Article Endpoint.
+ */
+class Article extends AbstractEndpoint
+{
+    /**
+     * @param array $filter = []
+     * 
+     * @return array|null
+     */
+    public function list(array $filter = []): ?array
+    {
+        $params = $this->addSession(['cFilter' => $filter]);
+        
+        $response = $this->soapClient->__soapCall('GetArtikelen', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        dump($processedResponse);
+        
+        if (isset($processedResponse['GetArtikelenResult']['Artikelen']['cArtikel'])) {
+            
+            return $this->returnList($processedResponse['GetArtikelenResult']['Artikelen']['cArtikel']);
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/Balance.php b/src/Endpoint/Endpoints/Balance.php
new file mode 100644
index 0000000..ce63150
--- /dev/null
+++ b/src/Endpoint/Endpoints/Balance.php
@@ -0,0 +1,53 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * Balance Endpoint.
+ */
+class Balance extends AbstractEndpoint
+{
+    /**
+     * @param array $filter = null
+     * 
+     * @return array|null
+     */
+    public function list(array $filter = []): ?array
+    {
+        $params = $this->addSession(['cFilter' => $filter]);
+        
+        $response = $this->soapClient->__soapCall('GetSaldi', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetSaldiResult']['Saldi']['cSaldo'])) {
+            
+            return $this->returnList($processedResponse['GetSaldiResult']['Saldi']['cSaldo']);
+        }
+        
+        return $processedResponse;
+    }
+    
+    /**
+     * @param array $filter = null
+     * 
+     * @return array|int|null
+     */
+    public function get(array $filter = [])
+    {
+        $params = $this->addSession(['cFilter' => $filter]);
+        
+        $response = $this->soapClient->__soapCall('GetSaldo', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetSaldoResult']['Saldo'])) {
+            
+            return $processedResponse['GetSaldoResult']['Saldo'];
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/CostCenter.php b/src/Endpoint/Endpoints/CostCenter.php
new file mode 100644
index 0000000..176ca1b
--- /dev/null
+++ b/src/Endpoint/Endpoints/CostCenter.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * Cost Center Endpoint.
+ */
+class CostCenter extends AbstractEndpoint
+{
+    /**
+     * @param array $filter = []
+     * 
+     * @return array|null
+     */
+    public function list(array $filter = []): ?array
+    {
+        $params = $this->addSession(['cFilter' => $filter]);
+        
+        $response = $this->soapClient->__soapCall('GetKostenplaatsen', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetKostenplaatsenResult']['Kostenplaatsen']['cKostenplaats'])) {
+            
+            return $this->returnList($processedResponse['GetKostenplaatsenResult']['Kostenplaatsen']['cKostenplaats']);
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/GeneralLedger.php b/src/Endpoint/Endpoints/GeneralLedger.php
new file mode 100644
index 0000000..9b66be8
--- /dev/null
+++ b/src/Endpoint/Endpoints/GeneralLedger.php
@@ -0,0 +1,76 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * General Ledger Endpoint.
+ */
+class GeneralLedger extends AbstractEndpoint
+{
+    /**
+     * @param array $filter = []
+     * 
+     * @return array|null
+     */
+    public function list(array $filter = []): ?array
+    {
+        $params = $this->addSession(['cFilter' => $filter]);
+        
+        $response = $this->soapClient->__soapCall('GetGrootboekrekeningen', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetGrootboekrekeningenResult']['Rekeningen']['cGrootboekrekening'])) {
+            
+            return $this->returnList($processedResponse['GetGrootboekrekeningenResult']['Rekeningen']['cGrootboekrekening']);
+        }
+        
+        return $processedResponse;
+    }
+    
+    /**
+     * @param array $data = []
+     * 
+     * @return array|int|null
+     */
+    public function create(array $data = [])
+    {
+        $params = $this->addSession(['oGb' => $data]);
+        
+        $response = $this->soapClient->__soapCall('AddGrootboekrekening', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (
+            isset($processedResponse['AddGrootboekrekeningResult']['Gb_ID'])
+            and !empty($processedResponse['AddGrootboekrekeningResult']['Gb_ID'])
+        ) {
+            return $processedResponse['AddGrootboekrekeningResult']['Gb_ID'];
+        }
+        
+        return $processedResponse;
+    }
+    
+    /**
+     * @param array $data = []
+     * 
+     * @return array|null
+     */
+    public function update(array $data = [])
+    {
+        $params = $this->addSession(['oGb' => $data]);
+        
+        $response = $this->soapClient->__soapCall('UpdateGrootboekrekening', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['UpdateGrootboekrekeningResult'])) {
+            
+            return $processedResponse['UpdateGrootboekrekeningResult'];
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/Invoice.php b/src/Endpoint/Endpoints/Invoice.php
new file mode 100644
index 0000000..8d0bf94
--- /dev/null
+++ b/src/Endpoint/Endpoints/Invoice.php
@@ -0,0 +1,55 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * Invoice Endpoint.
+ */
+class Invoice extends AbstractEndpoint
+{
+    /**
+     * @param array $filter = []
+     * 
+     * @return array|null
+     */
+    public function list(array $filter = []): ?array
+    {
+        $params = $this->addSession(['cFilter' => $filter]);
+        
+        $response = $this->soapClient->__soapCall('GetFacturen', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetFacturenResult']['Facturen']['cFactuurList'])) {
+            
+            return $this->returnList($processedResponse['GetFacturenResult']['Facturen']['cFactuurList']);
+        }
+        
+        return $processedResponse;
+    }
+    
+    /**
+     * @param array $data = []
+     * 
+     * @return array|string|null
+     */
+    public function create(array $data = [])
+    {
+        $params = $this->addSession(['oFact' => $data]);
+        
+        $response = $this->soapClient->__soapCall('AddFactuur', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (
+            isset($processedResponse['AddFactuurResult']['Factuurnummer'])
+            and !empty($processedResponse['AddFactuurResult']['Factuurnummer'])
+        ) {
+            return $processedResponse['AddFactuurResult']['Factuurnummer'];
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/Mutation.php b/src/Endpoint/Endpoints/Mutation.php
new file mode 100644
index 0000000..aedff46
--- /dev/null
+++ b/src/Endpoint/Endpoints/Mutation.php
@@ -0,0 +1,55 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * Mutation Endpoint.
+ */
+class Mutation extends AbstractEndpoint
+{
+    /**
+     * @param array $filter = []
+     * 
+     * @return array|null
+     */
+    public function list(array $filter = []): ?array
+    {
+        $params = $this->addSession(['cFilter' => $filter]);
+        
+        $response = $this->soapClient->__soapCall('GetMutaties', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetMutatiesResult']['Mutaties']['cMutatieList'])) {
+            
+            return $this->returnList($processedResponse['GetMutatiesResult']['Mutaties']['cMutatieList']);
+        }
+        
+        return $processedResponse;
+    }
+    
+    /**
+     * @param array $data = []
+     *
+     * @return array|string|null
+     */
+    public function create(array $data = [])
+    {
+        $params = $this->addSession(['oMut' => $data]);
+        
+        $response = $this->soapClient->__soapCall('AddMutatie', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (
+            isset($processedResponse['AddMutatieResult']['Mutatienummer'])
+            and !empty($processedResponse['AddMutatieResult']['Mutatienummer'])
+        ) {
+            return $processedResponse['AddMutatieResult']['Mutatienummer'];
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/OpenPost.php b/src/Endpoint/Endpoints/OpenPost.php
new file mode 100644
index 0000000..cb7a8fc
--- /dev/null
+++ b/src/Endpoint/Endpoints/OpenPost.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * Open Post Endpoint.
+ */
+class OpenPost extends AbstractEndpoint
+{
+    /**
+     * @param string $type = ''
+     * 
+     * @return array|null
+     */
+    public function list(string $type = ''): ?array
+    {
+        $params = $this->addSession(['OpSoort' => $type]);
+        
+        $response = $this->soapClient->__soapCall('GetOpenPosten', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetOpenPostenResult']['Openposten']['cOpenPost'])) {
+            
+            return $this->returnList($processedResponse['GetOpenPostenResult']['Openposten']['cOpenPost']);
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file
diff --git a/src/Endpoint/Endpoints/Relation.php b/src/Endpoint/Endpoints/Relation.php
new file mode 100644
index 0000000..b44ec3a
--- /dev/null
+++ b/src/Endpoint/Endpoints/Relation.php
@@ -0,0 +1,76 @@
+<?php
+
+namespace Onetoweb\Eboekhouden\Endpoint\Endpoints;
+
+use Onetoweb\Eboekhouden\Endpoint\AbstractEndpoint;
+
+/**
+ * Relation Endpoint.
+ */
+class Relation extends AbstractEndpoint
+{
+    /**
+     * @param array $filter = []
+     * 
+     * @return array|null
+     */
+    public function list(array $filter = []): ?array
+    {
+        $params = $this->addSession(['cFilter' => $filter]);
+        
+        $response = $this->soapClient->__soapCall('GetRelaties', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['GetRelatiesResult']['Relaties']['cRelatie'])) {
+            
+            return $this->returnList($processedResponse['GetRelatiesResult']['Relaties']['cRelatie']);
+        }
+        
+        return $processedResponse;
+    }
+    
+    /**
+     * @param array $data = []
+     *
+     * @return array|int|null
+     */
+    public function create(array $data = [])
+    {
+        $params = $this->addSession(['oRel' => $data]);
+        
+        $response = $this->soapClient->__soapCall('AddRelatie', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (
+            isset($processedResponse['AddRelatieResult']['Rel_ID'])
+            and !empty($processedResponse['AddRelatieResult']['Rel_ID'])
+        ) {
+            return $processedResponse['AddRelatieResult']['Rel_ID'];
+        }
+        
+        return $processedResponse;
+    }
+    
+    /**
+     * @param array $data = []
+     *
+     * @return array|int|null
+     */
+    public function update(array $data = [])
+    {
+        $params = $this->addSession(['oRel' => $data]);
+        
+        $response = $this->soapClient->__soapCall('UpdateRelatie', [$params]);
+        
+        $processedResponse = $this->proccessResponse($response);
+        
+        if (isset($processedResponse['UpdateRelatieResult'])) {
+            
+            return $processedResponse['UpdateRelatieResult'];
+        }
+        
+        return $processedResponse;
+    }
+}
\ No newline at end of file