diff --git a/src/GhostZero/BitinflowAccounts/ApiOperations/Delete.php b/src/GhostZero/BitinflowAccounts/ApiOperations/Delete.php
index 68d7393..d9926a4 100644
--- a/src/GhostZero/BitinflowAccounts/ApiOperations/Delete.php
+++ b/src/GhostZero/BitinflowAccounts/ApiOperations/Delete.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace GhostZero\BitinflowAccounts\ApiOperations;
 
 use GhostZero\BitinflowAccounts\Helpers\Paginator;
+use GhostZero\BitinflowAccounts\Result;
 
 /**
  * @author René Preuß <rene@preuss.io>
@@ -12,5 +13,5 @@ use GhostZero\BitinflowAccounts\Helpers\Paginator;
 trait Delete
 {
 
-    abstract public function delete(string $path = '', array $parameters = [], Paginator $paginator = null);
+    abstract public function delete(string $path = '', array $parameters = [], Paginator $paginator = null): Result;
 }
\ No newline at end of file
diff --git a/src/GhostZero/BitinflowAccounts/ApiOperations/Get.php b/src/GhostZero/BitinflowAccounts/ApiOperations/Get.php
index 6816961..ef2f1a3 100644
--- a/src/GhostZero/BitinflowAccounts/ApiOperations/Get.php
+++ b/src/GhostZero/BitinflowAccounts/ApiOperations/Get.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace GhostZero\BitinflowAccounts\ApiOperations;
 
 use GhostZero\BitinflowAccounts\Helpers\Paginator;
+use GhostZero\BitinflowAccounts\Result;
 
 /**
  * @author René Preuß <rene@preuss.io>
@@ -12,5 +13,5 @@ use GhostZero\BitinflowAccounts\Helpers\Paginator;
 trait Get
 {
 
-    abstract public function get(string $path = '', array $parameters = [], Paginator $paginator = null);
+    abstract public function get(string $path = '', array $parameters = [], Paginator $paginator = null): Result;
 }
\ No newline at end of file
diff --git a/src/GhostZero/BitinflowAccounts/ApiOperations/Post.php b/src/GhostZero/BitinflowAccounts/ApiOperations/Post.php
index 56c4c35..de10830 100644
--- a/src/GhostZero/BitinflowAccounts/ApiOperations/Post.php
+++ b/src/GhostZero/BitinflowAccounts/ApiOperations/Post.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace GhostZero\BitinflowAccounts\ApiOperations;
 
 use GhostZero\BitinflowAccounts\Helpers\Paginator;
+use GhostZero\BitinflowAccounts\Result;
 
 /**
  * @author René Preuß <rene@preuss.io>
@@ -12,5 +13,5 @@ use GhostZero\BitinflowAccounts\Helpers\Paginator;
 trait Post
 {
 
-    abstract public function post(string $path = '', array $parameters = [], Paginator $paginator = null);
+    abstract public function post(string $path = '', array $parameters = [], Paginator $paginator = null): Result;
 }
\ No newline at end of file
diff --git a/src/GhostZero/BitinflowAccounts/ApiOperations/Put.php b/src/GhostZero/BitinflowAccounts/ApiOperations/Put.php
index 03fc532..cb0f525 100644
--- a/src/GhostZero/BitinflowAccounts/ApiOperations/Put.php
+++ b/src/GhostZero/BitinflowAccounts/ApiOperations/Put.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace GhostZero\BitinflowAccounts\ApiOperations;
 
 use GhostZero\BitinflowAccounts\Helpers\Paginator;
+use GhostZero\BitinflowAccounts\Result;
 
 /**
  * @author René Preuß <rene@preuss.io>
@@ -12,5 +13,5 @@ use GhostZero\BitinflowAccounts\Helpers\Paginator;
 trait Put
 {
 
-    abstract public function put(string $path = '', array $parameters = [], Paginator $paginator = null);
+    abstract public function put(string $path = '', array $parameters = [], Paginator $paginator = null): Result;
 }
\ No newline at end of file
diff --git a/src/GhostZero/BitinflowAccounts/BitinflowAccounts.php b/src/GhostZero/BitinflowAccounts/BitinflowAccounts.php
index 43de378..1ea695d 100644
--- a/src/GhostZero/BitinflowAccounts/BitinflowAccounts.php
+++ b/src/GhostZero/BitinflowAccounts/BitinflowAccounts.php
@@ -18,12 +18,13 @@ class BitinflowAccounts
 {
 
     use Traits\ChargesTrait;
-    use Traits\CheckoutSessionsTrait;
+    use Traits\DocumentsTrait;
+    use Traits\PaymentIntentsTrait;
     use Traits\SshKeysTrait;
     use Traits\UsersTrait;
 
-    const BASE_URI = 'https://accounts.bitinflow.com/api/';
-    const OAUTH_BASE_URI = 'https://accounts.bitinflow.com/api/';
+    private const BASE_URI = 'https://accounts.bitinflow.com/api/';
+    private const OAUTH_BASE_URI = 'https://accounts.bitinflow.com/api/';
 
     /**
      * Guzzle is used to make http requests.
diff --git a/src/GhostZero/BitinflowAccounts/Enums/DocumentType.php b/src/GhostZero/BitinflowAccounts/Enums/DocumentType.php
new file mode 100644
index 0000000..fe53985
--- /dev/null
+++ b/src/GhostZero/BitinflowAccounts/Enums/DocumentType.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GhostZero\BitinflowAccounts\Enums;
+
+/**
+ * @author René Preuß <rene@preuss.io>
+ */
+class DocumentType
+{
+    // Read authorized user´s email address.
+    public const TYPE_PDF_INVOICE = 'pdf.invoice';
+
+    // Manage a authorized user object.
+    public const TYPE_PDF_ORDER = 'pdf.order';
+}
\ No newline at end of file
diff --git a/src/GhostZero/BitinflowAccounts/Enums/Scope.php b/src/GhostZero/BitinflowAccounts/Enums/Scope.php
index 0329c89..1e69375 100644
--- a/src/GhostZero/BitinflowAccounts/Enums/Scope.php
+++ b/src/GhostZero/BitinflowAccounts/Enums/Scope.php
@@ -15,24 +15,24 @@ class Scope
      */
 
     // Deprecated scope.
-    const API = 'api';
+    public const API = 'api';
 
     // Read nonpublic user information, including email address.
-    const READ_USER = 'read_user';
+    public const READ_USER = 'read_user';
 
     /*
      * v1 API
      */
 
     // Read authorized user´s email address.
-    const USERS_READ_EMAIL = 'users:read:email';
+    public const USERS_READ_EMAIL = 'users:read:email';
 
     // Manage a authorized user object.
-    const USERS_EDIT = 'users:edit';
+    public const USERS_EDIT = 'users:edit';
 
     // Read authorized user´s transactions.
-    const TRANSACTIONS_READ = 'transactions:read';
+    public const TRANSACTIONS_READ = 'transactions:read';
 
     // Create a new charge for the authorized user.
-    const CHARGES_CREATE = 'charges:create';
+    public const CHARGES_CREATE = 'charges:create';
 }
\ No newline at end of file
diff --git a/src/GhostZero/BitinflowAccounts/Traits/DocumentsTrait.php b/src/GhostZero/BitinflowAccounts/Traits/DocumentsTrait.php
new file mode 100644
index 0000000..5a7273e
--- /dev/null
+++ b/src/GhostZero/BitinflowAccounts/Traits/DocumentsTrait.php
@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GhostZero\BitinflowAccounts\Traits;
+
+use Carbon\CarbonInterface;
+use GhostZero\BitinflowAccounts\ApiOperations\Get;
+use GhostZero\BitinflowAccounts\ApiOperations\Post;
+use GhostZero\BitinflowAccounts\Result;
+
+/**
+ * @author René Preuß <rene@preuss.io>
+ */
+trait DocumentsTrait
+{
+
+    use Get, Post;
+
+    /**
+     * Create a Documents object
+     *
+     * @param array $parameters
+     *
+     * @return Result
+     */
+    public function createDocument(array $parameters): Result
+    {
+        return $this->post('documents', $parameters);
+    }
+
+    /**
+     * Create a Documents download url
+     *
+     * @param mixed                $identifier
+     * @param CarbonInterface|null $expiresAt
+     *
+     * @return Result
+     */
+    public function createDocumentDownloadUrl($identifier, ?CarbonInterface $expiresAt = null): Result
+    {
+        return $this->post("documents/$identifier/download-url", [
+            'expires_at' => $expiresAt
+                ? $expiresAt->toDateTimeString()
+                : now()->addHour()->toDateTimeString(),
+        ]);
+    }
+}
\ No newline at end of file
diff --git a/src/GhostZero/BitinflowAccounts/Traits/CheckoutSessionsTrait.php b/src/GhostZero/BitinflowAccounts/Traits/PaymentIntentsTrait.php
similarity index 60%
rename from src/GhostZero/BitinflowAccounts/Traits/CheckoutSessionsTrait.php
rename to src/GhostZero/BitinflowAccounts/Traits/PaymentIntentsTrait.php
index bd1dfbb..15e0410 100644
--- a/src/GhostZero/BitinflowAccounts/Traits/CheckoutSessionsTrait.php
+++ b/src/GhostZero/BitinflowAccounts/Traits/PaymentIntentsTrait.php
@@ -11,32 +11,32 @@ use GhostZero\BitinflowAccounts\Result;
 /**
  * @author René Preuß <rene@preuss.io>
  */
-trait CheckoutSessionsTrait
+trait PaymentIntentsTrait
 {
 
     use Get, Post;
 
     /**
-     * Get a Session object
+     * Get a Payment Intent object
      *
      * @param string $id
      *
      * @return Result         Result object
      */
-    public function getCheckoutSession(string $id): Result
+    public function getPaymentIntent(string $id): Result
     {
-        return $this->get("checkout/sessions/$id");
+        return $this->get("payment-intents/$id");
     }
 
     /**
-     * Create a Session object
+     * Create a Payment Intent object
      *
      * @param array $parameters
      *
      * @return Result
      */
-    public function createCheckoutSession(array $parameters): Result
+    public function createPaymentIntent(array $parameters): Result
     {
-        return $this->post('payments/sessions', $parameters);
+        return $this->post('payment-intents', $parameters);
     }
 }
\ No newline at end of file
diff --git a/tests/GhostZero/BitinflowAccounts/ApiChargesTest.php b/tests/GhostZero/BitinflowAccounts/ApiChargesTest.php
new file mode 100644
index 0000000..6904319
--- /dev/null
+++ b/tests/GhostZero/BitinflowAccounts/ApiChargesTest.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GhostZero\BitinflowAccounts\Tests;
+
+use GhostZero\BitinflowAccounts\Tests\TestCases\ApiTestCase;
+
+/**
+ * @author René Preuß <rene@preuss.io>
+ */
+class ApiChargesTest extends ApiTestCase
+{
+
+    public function testCaptureWithoutCapture(): void
+    {
+        $this->getClient()->withToken($this->getToken());
+
+        $result = $this->getClient()->createCharge([
+            'amount' => 2000,
+            'currency' => 'usd',
+            'source' => 'tok_visa',
+            'description' => 'Charge for jenny.rosen@example.com',
+        ]);
+        $this->registerResult($result);
+        $this->assertTrue($result->success());
+        $this->assertArrayHasKey('id', $result->data());
+        $this->assertEquals(2000, $result->data()->amount);
+        $this->assertTrue($result->data()->captured);
+    }
+
+    public function testChargeWithCapture(): void
+    {
+        $this->getClient()->withToken($this->getToken());
+
+        $result = $this->getClient()->createCharge([
+            'amount' => 2000,
+            'currency' => 'usd',
+            'source' => 'tok_visa',
+            'description' => 'Charge for jenny.rosen@example.com',
+            'capture' => false, // default is true for instant capture
+            'metadata' => [
+                'foo' => 'bar',
+            ],
+            'receipt_email' => 'rene+unittest@bitinflow.com',
+        ]);
+        $this->registerResult($result);
+        $this->assertTrue($result->success());
+        $this->assertArrayHasKey('id', $result->data());
+        $this->assertEquals(2000, $result->data()->amount);
+        $this->assertFalse($result->data()->captured);
+
+        $charge = $result->data();
+
+        $result = $this->getClient()->captureCharge($charge->id);
+        $this->registerResult($result);
+        $this->assertTrue($result->success());
+        $this->assertArrayHasKey('id', $result->data());
+        $this->assertEquals(2000, $result->data()->amount);
+        $this->assertTrue($result->data()->captured);
+    }
+}
\ No newline at end of file
diff --git a/tests/GhostZero/BitinflowAccounts/ApiDocumentsTest.php b/tests/GhostZero/BitinflowAccounts/ApiDocumentsTest.php
new file mode 100644
index 0000000..630c127
--- /dev/null
+++ b/tests/GhostZero/BitinflowAccounts/ApiDocumentsTest.php
@@ -0,0 +1,87 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GhostZero\BitinflowAccounts\Tests;
+
+use GhostZero\BitinflowAccounts\Enums\DocumentType;
+use GhostZero\BitinflowAccounts\Tests\TestCases\ApiTestCase;
+
+/**
+ * @author René Preuß <rene@preuss.io>
+ */
+class ApiDocumentsTest extends ApiTestCase
+{
+
+    public function testCreateDocument(): void
+    {
+        $this->getClient()->withToken($this->getToken());
+
+        $result = $this->getClient()->createDocument([
+            'branding' => [
+                'primary_color' => '#8284df',
+                'watermark_url' => 'https://fbs.streamkit.gg/img/pdf/wm.png',
+                'logo_url' => 'https://fbs.streamkit.gg/img/pdf/logo_dark_small.png',
+            ],
+            'locale' => 'de',
+            'type' => DocumentType::TYPE_PDF_INVOICE,
+            'data' => $this->createDummyInvoiceData(),
+            'receipt_email' => 'rene+unittest@bitinflow.com',
+        ]);
+
+        $this->registerResult($result);
+        $this->assertTrue($result->success());
+        $this->assertArrayHasKey('id', $result->data());
+        $this->assertArrayHasKey('download_url', $result->data());
+        $this->assertEquals(
+            'rene+unittest@bitinflow.com',
+            $result->data()->receipt_email
+        );
+    }
+
+    public function testGenerateDocumentStoragePath(): void
+    {
+        $this->getClient()->withToken($this->getToken());
+
+        $expiresAt = now()->addHours(2);
+
+        $result = $this->getClient()->createDocumentDownloadUrl(1, $expiresAt);
+
+        $this->registerResult($result);
+        $this->assertTrue($result->success());
+        $this->assertArrayHasKey('download_url', $result->data());
+        $this->assertEquals(
+            $expiresAt->toDateTimeString(),
+            $result->data()->expires_at
+        );
+    }
+
+    private function createDummyInvoiceData(): array
+    {
+        return [
+            'id' => 'FBS-IN-1337',
+            'customer' => [
+                'name' => 'GhostZero',
+                'email' => 'rene@preuss.io',
+                'address' => [
+                    'Example Street 123',
+                    '50733 Cologne',
+                    'GERMANY',
+                ],
+            ],
+            'line_items' => [
+                [
+                    'name' => 'T-shirt',
+                    'description' => 'Comfortable cotton t-shirt',
+                    'unit' => 'T-shirt', // optional unit name
+                    'amount' => 1500,
+                    'currency' => 'usd',
+                    'quantity' => 2,
+                ],
+            ],
+            'legal_notice' => 'According to the German §19 UStG no sales tax is calculated. However, the product is a digital good delivered via Internet we generally offer no refunds. The delivery date corresponds to the invoice date.',
+            'already_paid' => true,
+            'created_at' => now()->format('d.m.Y'),
+        ];
+    }
+}
\ No newline at end of file
diff --git a/tests/GhostZero/BitinflowAccounts/ApiPaymentIntentsTest.php b/tests/GhostZero/BitinflowAccounts/ApiPaymentIntentsTest.php
new file mode 100644
index 0000000..c611a16
--- /dev/null
+++ b/tests/GhostZero/BitinflowAccounts/ApiPaymentIntentsTest.php
@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GhostZero\BitinflowAccounts\Tests;
+
+use GhostZero\BitinflowAccounts\Tests\TestCases\ApiTestCase;
+
+/**
+ * @author René Preuß <rene@preuss.io>
+ */
+class ApiPaymentIntentsTest extends ApiTestCase
+{
+    private $paymentIntent;
+
+    public function testCreatePaymentIntent(): void
+    {
+        $this->getClient()->withToken($this->getToken());
+
+        $result = $this->getClient()->createPaymentIntent([
+            'payment_method_types' => ['card'],
+            'amount' => 1000,
+            'currency' => 'usd',
+            'application_fee_amount' => 123,
+        ]);
+        $this->registerResult($result);
+        $this->assertTrue($result->success());
+        $this->assertArrayHasKey('id', $result->data());
+        $this->assertArrayHasKey('redirect_url', $result->data());
+        $this->assertEquals(1000, $result->data()->amount);
+
+        // use this payment intent for our next tests
+        $this->paymentIntent = $result->data();
+    }
+
+    public function testGetPaymentIntent(): void
+    {
+        $this->getClient()->withToken($this->getToken());
+
+        $result = $this->getClient()->getPaymentIntent($this->paymentIntent->id);
+        $this->registerResult($result);
+        $this->assertTrue($result->success());
+        $this->assertArrayHasKey('id', $result->data());
+        $this->assertEquals(1000, $result->data()->amount);
+    }
+}
\ No newline at end of file
diff --git a/tests/GhostZero/BitinflowAccounts/ApiSshKeysTest.php b/tests/GhostZero/BitinflowAccounts/ApiSshKeysTest.php
index 16c08e7..9383e5b 100644
--- a/tests/GhostZero/BitinflowAccounts/ApiSshKeysTest.php
+++ b/tests/GhostZero/BitinflowAccounts/ApiSshKeysTest.php
@@ -13,15 +13,14 @@ use GhostZero\BitinflowAccounts\Tests\TestCases\ApiTestCase;
 class ApiSshKeysTest extends ApiTestCase
 {
 
-    public function testGetSshKeyByUserId()
+    public function testGetSshKeyByUserId(): void
     {
         $this->registerResult($result = $this->getClient()->getSshKeysByUserId(38));
-        $this->assertInstanceOf(Result::class, $result);
         $this->assertEquals('rene.preuss@check24.de', $result->shift()->name);
         $this->assertGreaterThanOrEqual(2, $result->count());
     }
 
-    public function testSshKeyManagement()
+    public function testSshKeyManagement(): void
     {
         $customName = 'Hello World!';
         $publicKey = 'ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAQEA3H7sYVrVCwwYIuRm3on3S9n/BCd2mBJrgCk6xTerbNmt0RyUZ+RtGsK6UYkgnRR2WWq9/Pv2s3RXJXPxbsIEYmKCcTdLUvDk56x9385cIVUX4w016mpe/8lyu+mIdqWYKsJMoab0oReCDX8Y9qBcaffDh8AgmYVN+86gXgoP1ITe9BDYrFiR6U571VyLDVN3OYOYPMF3/L9f0knMfM0T4LrS8oi6faVBCxZHRoBGtGmsTBkE0KwplYQFN2aa4Mxab+rTUFmJr3LYEcJF0J8wNJ3eEDFNOR0254jrjbGGAXGsc+cxJoNzech+GBkRMKMpNU0lds6VxP0ZB25VfzjEmQ== René Preuß';
diff --git a/tests/GhostZero/BitinflowAccounts/ApiUsersTest.php b/tests/GhostZero/BitinflowAccounts/ApiUsersTest.php
index f239a6f..735671a 100644
--- a/tests/GhostZero/BitinflowAccounts/ApiUsersTest.php
+++ b/tests/GhostZero/BitinflowAccounts/ApiUsersTest.php
@@ -4,7 +4,6 @@ declare(strict_types=1);
 
 namespace GhostZero\BitinflowAccounts\Tests;
 
-use GhostZero\BitinflowAccounts\Result;
 use GhostZero\BitinflowAccounts\Tests\TestCases\ApiTestCase;
 
 /**
@@ -13,11 +12,10 @@ use GhostZero\BitinflowAccounts\Tests\TestCases\ApiTestCase;
 class ApiUsersTest extends ApiTestCase
 {
 
-    public function testGetAuthedUser()
+    public function testGetAuthedUser(): void
     {
         $this->getClient()->withToken($this->getToken());
         $this->registerResult($result = $this->getClient()->getAuthedUser());
-        $this->assertInstanceOf(Result::class, $result);
         $this->assertEquals('rene@preuss.io', $result->data()->email);
     }
 }
\ No newline at end of file
diff --git a/tests/GhostZero/BitinflowAccounts/ServiceInstantiationTest.php b/tests/GhostZero/BitinflowAccounts/ServiceInstantiationTest.php
index 293dac8..c9165d3 100644
--- a/tests/GhostZero/BitinflowAccounts/ServiceInstantiationTest.php
+++ b/tests/GhostZero/BitinflowAccounts/ServiceInstantiationTest.php
@@ -14,12 +14,12 @@ use GhostZero\BitinflowAccounts\Tests\TestCases\TestCase;
 class ServiceInstantiationTest extends TestCase
 {
 
-    public function testInstance()
+    public function testInstance(): void
     {
         $this->assertInstanceOf(BitinflowAccounts::class, app(BitinflowAccounts::class));
     }
 
-    public function testFacade()
+    public function testFacade(): void
     {
         $this->assertInstanceOf(BitinflowAccounts::class, BitinflowAccountsFacade::getFacadeRoot());
     }