diff --git a/composer.json b/composer.json
index 62ee1cf..19442b1 100644
--- a/composer.json
+++ b/composer.json
@@ -2,7 +2,7 @@
     "name": "payvision/payvision-sdk-php",
     "description": "Payvision PHP SDK",
     "type": "library",
-    "version": "5.0.0",
+    "version": "5.1.0",
     "license": "MIT",
     "require": {
         "php": "^7.2.5|^7.3",
diff --git a/src/Domain/Checkouts/Service/Builder/Error.php b/src/Domain/Checkouts/Service/Builder/Error.php
index 63f962f..b01b60a 100644
--- a/src/Domain/Checkouts/Service/Builder/Error.php
+++ b/src/Domain/Checkouts/Service/Builder/Error.php
@@ -42,6 +42,15 @@ public function setMessage(string $message): Error
         return $this->set('message', $message);
     }
 
+    /**
+     * @param string $detailedMessage
+     * @return Error
+     */
+    public function setDetailedMessage(string $detailedMessage): Error
+    {
+        return $this->set('detailedMessage', $detailedMessage);
+    }
+
     /**
      * @return ErrorObject
      */
@@ -49,7 +58,8 @@ protected function buildObject(): ErrorObject
     {
         return new ErrorObject(
             $this->get('code'),
-            $this->get('message')
+            $this->get('message'),
+            $this->get('detailedMessage')
         );
     }
 }
diff --git a/src/Domain/Checkouts/ValueObject/Error.php b/src/Domain/Checkouts/ValueObject/Error.php
index 06e2057..2275fa5 100644
--- a/src/Domain/Checkouts/ValueObject/Error.php
+++ b/src/Domain/Checkouts/ValueObject/Error.php
@@ -23,18 +23,26 @@ class Error
      */
     private $message;
 
+    /**
+     * @var string
+     */
+    private $detailedMessage;
+
     /**
      * Error constructor.
      *
      * @param int $code
      * @param string $message
+     * @param string $detailedMessage
      */
     public function __construct(
         int $code,
-        string $message
+        string $message,
+        string $detailedMessage = null
     ) {
         $this->code = $code;
         $this->message = $message;
+        $this->detailedMessage = $detailedMessage;
     }
 
     /**
@@ -52,4 +60,12 @@ public function getMessage(): string
     {
         return $this->message;
     }
+
+    /**
+     * @return string|null
+     */
+    public function getDetailedMessage(): ?string
+    {
+        return $this->detailedMessage;
+    }
 }
diff --git a/src/Domain/Paymentlinks/Service/Builder/Error.php b/src/Domain/Paymentlinks/Service/Builder/Error.php
index 11fc52b..45d575c 100644
--- a/src/Domain/Paymentlinks/Service/Builder/Error.php
+++ b/src/Domain/Paymentlinks/Service/Builder/Error.php
@@ -42,6 +42,15 @@ public function setMessage(string $message): Error
         return $this->set('message', $message);
     }
 
+    /**
+     * @param string $detailedMessage
+     * @return Error
+     */
+    public function setDetailedMessage(string $detailedMessage): Error
+    {
+        return $this->set('detailedMessage', $detailedMessage);
+    }
+
     /**
      * @return ErrorObject
      */
@@ -49,7 +58,8 @@ protected function buildObject(): ErrorObject
     {
         return new ErrorObject(
             $this->get('code'),
-            $this->get('message')
+            $this->get('message'),
+            $this->get('detailedMessage')
         );
     }
 }
diff --git a/src/Domain/Paymentlinks/Service/Builder/Link/ResponsePaymentError.php b/src/Domain/Paymentlinks/Service/Builder/Link/ResponsePaymentError.php
index 1f44b93..1bbef08 100644
--- a/src/Domain/Paymentlinks/Service/Builder/Link/ResponsePaymentError.php
+++ b/src/Domain/Paymentlinks/Service/Builder/Link/ResponsePaymentError.php
@@ -42,6 +42,15 @@ public function setMessage(string $message): ResponsePaymentError
         return $this->set('message', $message);
     }
 
+    /**
+     * @param string $detailedMessage
+     * @return ResponsePaymentError
+     */
+    public function setDetailedMessage(string $detailedMessage): ResponsePaymentError
+    {
+        return $this->set('detailedMessage', $detailedMessage);
+    }
+
     /**
      * @return ResponsePaymentErrorObject
      */
@@ -49,7 +58,8 @@ protected function buildObject(): ResponsePaymentErrorObject
     {
         return new ResponsePaymentErrorObject(
             $this->get('code'),
-            $this->get('message')
+            $this->get('message'),
+            $this->get('detailedMessage')
         );
     }
 }
diff --git a/src/Domain/Paymentlinks/ValueObject/Error.php b/src/Domain/Paymentlinks/ValueObject/Error.php
index 9f0fd2a..a47fb8d 100644
--- a/src/Domain/Paymentlinks/ValueObject/Error.php
+++ b/src/Domain/Paymentlinks/ValueObject/Error.php
@@ -23,18 +23,26 @@ class Error
      */
     private $message;
 
+    /**
+     * @var string
+     */
+    private $detailedMessage;
+
     /**
      * Error constructor.
      *
      * @param int $code
      * @param string $message
+     * @param string $detailedMessage
      */
     public function __construct(
         int $code,
-        string $message
+        string $message,
+        string $detailedMessage = null
     ) {
         $this->code = $code;
         $this->message = $message;
+        $this->detailedMessage = $detailedMessage;
     }
 
     /**
@@ -52,4 +60,12 @@ public function getMessage(): string
     {
         return $this->message;
     }
+
+    /**
+     * @return string|null
+     */
+    public function getDetailedMessage(): ?string
+    {
+        return $this->detailedMessage;
+    }
 }
diff --git a/src/Domain/Paymentlinks/ValueObject/Link/ResponsePaymentError.php b/src/Domain/Paymentlinks/ValueObject/Link/ResponsePaymentError.php
index 98a0b6a..988a9d8 100644
--- a/src/Domain/Paymentlinks/ValueObject/Link/ResponsePaymentError.php
+++ b/src/Domain/Paymentlinks/ValueObject/Link/ResponsePaymentError.php
@@ -23,18 +23,26 @@ class ResponsePaymentError
      */
     private $message;
 
+    /**
+     * @var string
+     */
+    private $detailedMessage;
+
     /**
      * ResponsePaymentError constructor.
      *
      * @param int $code
      * @param string $message
+     * @param string $detailedMessage
      */
     public function __construct(
         int $code,
-        string $message
+        string $message,
+        string $detailedMessage = null
     ) {
         $this->code = $code;
         $this->message = $message;
+        $this->detailedMessage = $detailedMessage;
     }
 
     /**
@@ -52,4 +60,12 @@ public function getMessage(): string
     {
         return $this->message;
     }
+
+    /**
+     * @return string|null
+     */
+    public function getDetailedMessage(): ?string
+    {
+        return $this->detailedMessage;
+    }
 }
diff --git a/src/Domain/Payments/Service/Builder/Error.php b/src/Domain/Payments/Service/Builder/Error.php
index 9d51601..f6edcf6 100644
--- a/src/Domain/Payments/Service/Builder/Error.php
+++ b/src/Domain/Payments/Service/Builder/Error.php
@@ -42,6 +42,15 @@ public function setMessage(string $message): Error
         return $this->set('message', $message);
     }
 
+    /**
+     * @param string $detailedMessage
+     * @return Error
+     */
+    public function setDetailedMessage(string $detailedMessage): Error
+    {
+        return $this->set('detailedMessage', $detailedMessage);
+    }
+
     /**
      * @return ErrorObject
      */
@@ -49,7 +58,8 @@ protected function buildObject(): ErrorObject
     {
         return new ErrorObject(
             $this->get('code'),
-            $this->get('message')
+            $this->get('message'),
+            $this->get('detailedMessage')
         );
     }
 }
diff --git a/src/Domain/Payments/ValueObject/Error.php b/src/Domain/Payments/ValueObject/Error.php
index e40b2ed..bd7d297 100644
--- a/src/Domain/Payments/ValueObject/Error.php
+++ b/src/Domain/Payments/ValueObject/Error.php
@@ -23,18 +23,26 @@ class Error
      */
     private $message;
 
+    /**
+     * @var string
+     */
+    private $detailedMessage;
+
     /**
      * Error constructor.
      *
      * @param int $code
      * @param string $message
+     * @param string $detailedMessage
      */
     public function __construct(
         int $code,
-        string $message
+        string $message,
+        string $detailedMessage = null
     ) {
         $this->code = $code;
         $this->message = $message;
+        $this->detailedMessage = $detailedMessage;
     }
 
     /**
@@ -52,4 +60,12 @@ public function getMessage(): string
     {
         return $this->message;
     }
+
+    /**
+     * @return string|null
+     */
+    public function getDetailedMessage(): ?string
+    {
+        return $this->detailedMessage;
+    }
 }
diff --git a/src/Domain/Service/Helper/AfterpayErrorMessageHelper.php b/src/Domain/Service/Helper/AfterpayErrorMessageHelper.php
new file mode 100644
index 0000000..502c06a
--- /dev/null
+++ b/src/Domain/Service/Helper/AfterpayErrorMessageHelper.php
@@ -0,0 +1,85 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright Copyright (c) 2018-2020 Payvision B.V. (https://www.payvision.com/)
+ * @license see LICENCE.TXT
+ */
+
+namespace Payvision\SDK\Domain\Service\Helper;
+
+use Payvision\SDK\Exception\AfterpayErrorException;
+
+class AfterpayErrorMessageHelper
+{
+    public const BILLTO_CITY_MISSING = 'billto.city.missing';
+    public const BILLTO_HOUSENUMBER_INVALID = 'billto.housenumber.invalid';
+    public const BILLTO_HOUSENUMBER_MISSING = 'billto.housenumber.missing';
+    public const BILLTO_HOUSENUMBERADDITION_INVALID = 'billto.housenumberaddition.invalid';
+    public const BILLTO_HOUSENUMBERADDITION_MISSING = 'billto.housenumberaddition.missing';
+    public const BILLTO_ISOCOUNTRYCODE_INVALID = 'billto.isocountrycode.invalid';
+    public const BILLTO_ISOCOUNTRYCODE_MISSING = 'billto.isocountrycode.missing';
+    public const BILLTO_ISOLANGUAGE_MISSING = 'billto.isolanguage.missing';
+    public const BILLTO_PERSON_DATEOFBIRTH_INVALID = 'billto.person.dateofbirth.invalid';
+    public const BILLTO_PERSON_EMAILADDRESS_INVALID = 'billto.person.emailaddress.invalid';
+    public const BILLTO_PERSON_EMAILADDRESS_MISSING = 'billto.person.emailaddress.missing';
+    public const BILLTO_PERSON_GENDER_INVALID = 'billto.person.gender.invalid';
+    public const BILLTO_PERSON_GENDER_MISSING = 'billto.person.gender.missing';
+    public const BILLTO_PERSON_INITIALS_INVALID = 'billto.person.initials.invalid';
+    public const BILLTO_PERSON_INITIALS_MISSING = 'billto.person.initials.missing';
+    public const BILLTO_PERSON_LASTNAME_INVALID = 'billto.person.lastname.invalid';
+    public const BILLTO_PERSON_LASTNAME_MISSING = 'billto.person.lastname.missing';
+    public const BILLTO_PERSON_PREFIX_INVALID = 'billto.person.prefix.invalid';
+    public const BILLTO_PERSON_PREFIX_MISSING = 'billto.person.prefix.missing';
+    public const BILLTO_PHONENUMBER1_INVALID = 'billto.phonenumber1.invalid';
+    public const BILLTO_PHONENUMBER1_MISSING = 'billto.phonenumber1.missing';
+    public const BILLTO_PHONENUMBER2_INVALID = 'billto.phonenumber2.invalid';
+    public const BILLTO_PHONENUMBER2_MISSING = 'billto.phonenumber2.missing';
+    public const BILLTO_POSTALCODE_INVALID = 'billto.postalcode.invalid';
+    public const BILLTO_POSTALCODE_MISSING = 'billto.postalcode.missing';
+    public const BILLTO_STREETNAME_MISSING = 'billto.streetname.missing';
+    public const SHIPTO_HOUSENUMBER_INVALID = 'shipto.housenumber.invalid';
+    public const SHIPTO_HOUSENUMBER_MISSING = 'shipto.housenumber.missing';
+    public const SHIPTO_HOUSENUMBERADDITION_INVALID = 'shipto.housenumberaddition.invalid';
+    public const SHIPTO_HOUSENUMBERADDITION_MISSING = 'shipto.housenumberaddition.missing';
+    public const SHIPTO_ISOCOUNTRYCODE_INVALID = 'shipto.isocountrycode.invalid';
+    public const SHIPTO_ISOCOUNTRYCODE_MISSING = 'shipto.isocountrycode.missing';
+    public const SHIPTO_ISOLANGUAGE_MISSING = 'shipto.isolanguage.missing';
+    public const SHIPTO_PERSON_GENDER_INVALID = 'shipto.person.gender.invalid';
+    public const SHIPTO_PERSON_GENDER_MISSING = 'shipto.person.gender.missing';
+    public const SHIPTO_PERSON_INITIALS_INVALID = 'shipto.person.initials.invalid';
+    public const SHIPTO_PERSON_INITIALS_MISSING = 'shipto.person.initials.missing';
+    public const SHIPTO_PERSON_LASTNAME_MISSING = 'shipto.person.lastname.missing';
+    public const SHIPTO_PERSON_PREFIX_INVALID = 'shipto.person.prefix.invalid';
+    public const SHIPTO_PERSON_PREFIX_MISSING = 'shipto.person.prefix.missing';
+    public const SHIPTO_POSTALCODE_INVALID = 'shipto.postalcode.invalid';
+    public const SHIPTO_POSTALCODE_MISSING = 'shipto.postalcode.missing';
+    public const SHIPTO_STREETNAME_MISSING = 'shipto.streetname.missing';
+
+    /**
+     * @param string $errorDetail
+     * @return array
+     * @throws AfterpayErrorException
+     */
+    public static function extractMessageCodes(string $errorDetail): array
+    {
+        $result = [];
+        $messages = \explode('|', $errorDetail);
+        foreach ($messages as $message) {
+            $result[] = self::extractMessageCode(\trim($message));
+        }
+        return $result;
+    }
+
+    /**
+     * @throws AfterpayErrorException
+     */
+    protected static function extractMessageCode(string $message): string
+    {
+        if (\preg_match('/^(field\.)?(?P<code>[a-z]+\.[a-z.]+)/', $message, $matches)) {
+            return $matches['code'];
+        }
+        throw new AfterpayErrorException('Unable to handle Afterpay error code: ' . $message);
+    }
+}
diff --git a/src/Exception/AfterpayErrorException.php b/src/Exception/AfterpayErrorException.php
new file mode 100644
index 0000000..be8f909
--- /dev/null
+++ b/src/Exception/AfterpayErrorException.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright Copyright (c) 2018-2020 Payvision B.V. (https://www.payvision.com/)
+ * @license see LICENCE.TXT
+ */
+
+namespace Payvision\SDK\Exception;
+
+use Exception;
+
+class AfterpayErrorException extends Exception
+{
+}
diff --git a/src/Exception/ApiException.php b/src/Exception/ApiException.php
index e85af95..064e388 100644
--- a/src/Exception/ApiException.php
+++ b/src/Exception/ApiException.php
@@ -13,9 +13,9 @@
 
 class ApiException extends Exception
 {
-    const RESPONSE_CLASS_NOT_FOUND = 1100;
-    const CANNOT_BUILD_RESPONSE = 1101;
-    const INVALID_REQUEST_METHOD = 1102;
-    const RESPONSE_CLASS_NOT_SET = 1103;
-    const INVALID_RESPONSE = 1104;
+    public const RESPONSE_CLASS_NOT_FOUND = 1100;
+    public const CANNOT_BUILD_RESPONSE = 1101;
+    public const INVALID_REQUEST_METHOD = 1102;
+    public const RESPONSE_CLASS_NOT_SET = 1103;
+    public const INVALID_RESPONSE = 1104;
 }
diff --git a/src/Exception/DataTypeException.php b/src/Exception/DataTypeException.php
index 2be1704..b198d2a 100644
--- a/src/Exception/DataTypeException.php
+++ b/src/Exception/DataTypeException.php
@@ -13,11 +13,11 @@
 
 class DataTypeException extends Exception
 {
-    const UNKNOWN_COUNTRY = 3100;
-    const UNKNOWN_CURRENCY = 3101;
-    const UNKNOWN_LANGUAGE = 3102;
-    const AMOUNT_CANNOT_BE_NEGATIVE = 3103;
-    const STRING_TOO_LONG = 3104;
-    const VALUE_NOT_ALLOWED = 3105;
-    const INVALID_URL = 3106;
+    public const UNKNOWN_COUNTRY = 3100;
+    public const UNKNOWN_CURRENCY = 3101;
+    public const UNKNOWN_LANGUAGE = 3102;
+    public const AMOUNT_CANNOT_BE_NEGATIVE = 3103;
+    public const STRING_TOO_LONG = 3104;
+    public const VALUE_NOT_ALLOWED = 3105;
+    public const INVALID_URL = 3106;
 }
diff --git a/src/Exception/RepositoryException.php b/src/Exception/RepositoryException.php
index ddf81cf..5bf9ae3 100644
--- a/src/Exception/RepositoryException.php
+++ b/src/Exception/RepositoryException.php
@@ -13,5 +13,5 @@
 
 class RepositoryException extends Exception
 {
-    const FILE_NOT_FOUND = 4100;
+    public const FILE_NOT_FOUND = 4100;
 }
diff --git a/src/Exception/WebhookException.php b/src/Exception/WebhookException.php
index 97ef16c..20e0a8d 100644
--- a/src/Exception/WebhookException.php
+++ b/src/Exception/WebhookException.php
@@ -13,9 +13,9 @@
 
 class WebhookException extends Exception
 {
-    const UNKNOWN_PAYLOAD = 5100;
-    const UNEXPECTED_PAYLOAD = 5101;
-    const JWT_NOT_VALIDATED = 5102;
-    const VALIDATION_FAILED = 5103;
-    const MISSING_CHECKSUM = 5104;
+    public const UNKNOWN_PAYLOAD = 5100;
+    public const UNEXPECTED_PAYLOAD = 5101;
+    public const JWT_NOT_VALIDATED = 5102;
+    public const VALIDATION_FAILED = 5103;
+    public const MISSING_CHECKSUM = 5104;
 }
diff --git a/tests/Test/Unit/Domain/Service/Helper/AfterpayErrorMessageHelperTest.php b/tests/Test/Unit/Domain/Service/Helper/AfterpayErrorMessageHelperTest.php
new file mode 100644
index 0000000..79d75d7
--- /dev/null
+++ b/tests/Test/Unit/Domain/Service/Helper/AfterpayErrorMessageHelperTest.php
@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright Copyright (c) 2018-2020 Payvision B.V. (https://www.payvision.com/)
+ * @license see LICENCE.TXT
+ */
+
+namespace Payvision\SDK\Test\Unit\Domain\Service\Helper;
+
+use Exception;
+use Payvision\SDK\Domain\Service\Helper\AfterpayErrorMessageHelper;
+use Payvision\SDK\Exception\AfterpayErrorException;
+use PHPUnit\Framework\TestCase;
+
+class AfterpayErrorMessageHelperTest extends TestCase
+{
+    /**
+     * @param string $errorCode
+     * @param array $expected
+     * @throws AfterpayErrorException
+     * @dataProvider afterpayExtractMessageCodeProvider
+     */
+    public function testExtractMessageCodes(string $errorCode, array $expected): void
+    {
+        self::assertSame($expected, AfterpayErrorMessageHelper::extractMessageCodes($errorCode));
+    }
+
+    public function afterpayExtractMessageCodeProvider(): array
+    {
+        return [
+            'single error code' => [
+                'field.billto.city.missing (De plaatsnaam van het factuuradres ontbreekt)',
+                [AfterpayErrorMessageHelper::BILLTO_CITY_MISSING],
+            ],
+            'multiple error codes' => [
+                'field.billto.housenumber.missing (Het huisnummer van het factuuradres ontbreekt) | ' .
+                'field.billto.housenumberaddition.missing (De huisnummertoevoeging van het factuuradres ontbreekt)',
+                [
+                    AfterpayErrorMessageHelper::BILLTO_HOUSENUMBER_MISSING,
+                    AfterpayErrorMessageHelper::BILLTO_HOUSENUMBERADDITION_MISSING,
+                ],
+            ],
+        ];
+    }
+
+    /**
+     * @param string $message
+     * @param string $expected
+     * @throws AfterpayErrorException
+     * @dataProvider afterpayExtractMessageCodeExceptionProvider
+     */
+    public function testExtractMessageCodesException(string $message, string $expected): void
+    {
+        $this->expectException(AfterpayErrorException::class);
+        try {
+            AfterpayErrorMessageHelper::extractMessageCodes($message);
+        } catch (Exception $exception) {
+            self::assertSame($expected, $exception->getMessage());
+            throw $exception;
+        }
+    }
+
+    public function afterpayExtractMessageCodeExceptionProvider(): array
+    {
+        return [
+            'Non parsable error code' => [
+                'housenumberaddition_missing',
+                'Unable to handle Afterpay error code: housenumberaddition_missing',
+            ]
+        ];
+    }
+}