diff --git a/examples/sales-invoices/create-sales-invoice.php b/examples/sales-invoices/create-sales-invoice.php
index a3a4aed1..69f93a84 100644
--- a/examples/sales-invoices/create-sales-invoice.php
+++ b/examples/sales-invoices/create-sales-invoice.php
@@ -1,5 +1,6 @@
 <?php
 
+use Mollie\Api\Types\PaymentTerm;
 use Mollie\Api\Types\SalesInvoiceStatus;
 
 /*
@@ -20,7 +21,7 @@
         'status' => SalesInvoiceStatus::DRAFT,
         'vatScheme' => 'standard',
         'vatMode' => 'inclusive',
-        'paymentTerm' => '30 days',
+        'paymentTerm' => PaymentTerm::DAYS_30,
         'recipientIdentifier' => 'XXXXX',
         'recipient' => [
             'type' => 'consumer',
diff --git a/src/Types/PaymentTerm.php b/src/Types/PaymentTerm.php
new file mode 100644
index 00000000..7691a2e0
--- /dev/null
+++ b/src/Types/PaymentTerm.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Mollie\Api\Types;
+
+class PaymentTerm
+{
+    const DAYS_7 = '7 days';
+
+    const DAYS_14 = '14 days';
+
+    const DAYS_30 = '30 days';
+
+    const DAYS_45 = '45 days';
+
+    const DAYS_60 = '60 days';
+
+    const DAYS_90 = '90 days';
+
+    const DAYS_120 = '120 days';
+}