diff --git a/sample/doc/assets/behavior.js b/sample/doc/assets/behavior.js
index c955ee2..180ecc5 100644
--- a/sample/doc/assets/behavior.js
+++ b/sample/doc/assets/behavior.js
@@ -118,45 +118,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "billing/CreatePlan",
             "title": "CreatePlan"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Create Plan Sample",
-                "slug": "create-plan-sample"
-              },
-              "depth": 1
-            }, {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Basic Information",
-                "slug": "basic-information"
-              },
-              "depth": 1
-            }, {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Payment definitions for this billing plan.",
-                "slug": "payment-definitions-for-this-billing-plan"
-              },
-              "depth": 1,
-              "children": [
-                {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Create Plan",
-                    "slug": "create-plan"
-                  },
-                  "depth": 3
-                }
-              ]
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
@@ -336,29 +298,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "billing/UpdatePlan",
             "title": "UpdatePlan"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Update a plan",
-                "slug": "update-a-plan"
-              },
-              "depth": 1,
-              "children": [
-                {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Making Plan Active",
-                    "slug": "making-plan-active"
-                  },
-                  "depth": 3
-                }
-              ]
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
@@ -422,7 +362,112 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "invoice/CreateInvoice",
             "title": "CreateInvoice"
           },
-          "depth": 2
+          "depth": 2,
+          "outline": [
+            {
+              "type": "heading",
+              "data": {
+                "level": 1,
+                "title": "Create Invoice Sample",
+                "slug": "create-invoice-sample"
+              },
+              "depth": 1,
+              "children": [
+                {
+                  "type": "heading",
+                  "data": {
+                    "level": 3,
+                    "title": "Invoice Info",
+                    "slug": "invoice-info"
+                  },
+                  "depth": 3
+                }, {
+                  "type": "heading",
+                  "data": {
+                    "level": 3,
+                    "title": "Merchant Info",
+                    "slug": "merchant-info"
+                  },
+                  "depth": 3
+                }, {
+                  "type": "heading",
+                  "data": {
+                    "level": 3,
+                    "title": "Address Information",
+                    "slug": "address-information"
+                  },
+                  "depth": 3
+                }, {
+                  "type": "heading",
+                  "data": {
+                    "level": 3,
+                    "title": "Billing Information",
+                    "slug": "billing-information"
+                  },
+                  "depth": 3
+                }, {
+                  "type": "heading",
+                  "data": {
+                    "level": 3,
+                    "title": "Items List",
+                    "slug": "items-list"
+                  },
+                  "depth": 3,
+                  "children": [
+                    {
+                      "type": "heading",
+                      "data": {
+                        "level": 4,
+                        "title": "Tax Item",
+                        "slug": "tax-item"
+                      },
+                      "depth": 4
+                    }, {
+                      "type": "heading",
+                      "data": {
+                        "level": 4,
+                        "title": "Tax Item",
+                        "slug": "tax-item"
+                      },
+                      "depth": 4
+                    }, {
+                      "type": "heading",
+                      "data": {
+                        "level": 4,
+                        "title": "Final Discount",
+                        "slug": "final-discount"
+                      },
+                      "depth": 4
+                    }
+                  ]
+                }, {
+                  "type": "heading",
+                  "data": {
+                    "level": 3,
+                    "title": "Shipping Information",
+                    "slug": "shipping-information"
+                  },
+                  "depth": 3
+                }, {
+                  "type": "heading",
+                  "data": {
+                    "level": 3,
+                    "title": "Logo",
+                    "slug": "logo"
+                  },
+                  "depth": 3
+                }, {
+                  "type": "heading",
+                  "data": {
+                    "level": 3,
+                    "title": "Create Invoice",
+                    "slug": "create-invoice"
+                  },
+                  "depth": 3
+                }
+              ]
+            }
+          ]
         }, {
           "type": "file",
           "data": {
@@ -1156,93 +1201,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "payments/CreatePaymentUsingPayPal",
             "title": "CreatePaymentUsingPayPal"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Create Payment using PayPal as payment method",
-                "slug": "create-payment-using-paypal-as-payment-method"
-              },
-              "depth": 1,
-              "children": [
-                {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Payer",
-                    "slug": "payer"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Itemized information",
-                    "slug": "itemized-information"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Additional payment details",
-                    "slug": "additional-payment-details"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Amount",
-                    "slug": "amount"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Transaction",
-                    "slug": "transaction"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Redirect urls",
-                    "slug": "redirect-urls"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Payment",
-                    "slug": "payment"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Create Payment",
-                    "slug": "create-payment"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Get redirect url",
-                    "slug": "get-redirect-url"
-                  },
-                  "depth": 3
-                }
-              ]
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
@@ -1260,93 +1219,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "payments/CreatePaymentUsingSavedCard",
             "title": "CreatePaymentUsingSavedCard"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Create payment using a saved credit card",
-                "slug": "create-payment-using-a-saved-credit-card"
-              },
-              "depth": 1,
-              "children": [
-                {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Credit card token",
-                    "slug": "credit-card-token"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "FundingInstrument",
-                    "slug": "fundinginstrument"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Payer",
-                    "slug": "payer"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Itemized information",
-                    "slug": "itemized-information"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Additional payment details",
-                    "slug": "additional-payment-details"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Amount",
-                    "slug": "amount"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Transaction",
-                    "slug": "transaction"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Payment",
-                    "slug": "payment"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Create Payment",
-                    "slug": "create-payment"
-                  },
-                  "depth": 3
-                }
-              ]
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
@@ -1364,37 +1237,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "payments/ExecutePayment",
             "title": "ExecutePayment"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Execute Payment Sample",
-                "slug": "execute-payment-sample"
-              },
-              "depth": 1,
-              "children": [
-                {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Approval Status",
-                    "slug": "approval-status"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Payment Execute",
-                    "slug": "payment-execute"
-                  },
-                  "depth": 3
-                }
-              ]
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
@@ -1448,29 +1291,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "payments/GetPayment",
             "title": "GetPayment"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "GetPaymentSample",
-                "slug": "getpaymentsample"
-              },
-              "depth": 1,
-              "children": [
-                {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Retrieve payment",
-                    "slug": "retrieve-payment"
-                  },
-                  "depth": 3
-                }
-              ]
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
@@ -1488,29 +1309,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "payments/ListPayments",
             "title": "ListPayments"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "GetPaymentList",
-                "slug": "getpaymentlist"
-              },
-              "depth": 1,
-              "children": [
-                {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Retrieve payment",
-                    "slug": "retrieve-payment"
-                  },
-                  "depth": 3
-                }
-              ]
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
@@ -1546,53 +1345,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "payments/OrderCapture",
             "title": "OrderCapture"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Capture Order Sample",
-                "slug": "capture-order-sample"
-              },
-              "depth": 1,
-              "children": [
-                {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Approval Status",
-                    "slug": "approval-status"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Retrieve the order",
-                    "slug": "retrieve-the-order"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Create Capture Object",
-                    "slug": "create-capture-object"
-                  },
-                  "depth": 3
-                }, {
-                  "type": "heading",
-                  "data": {
-                    "level": 3,
-                    "title": "Capture Order",
-                    "slug": "capture-order"
-                  },
-                  "depth": 3
-                }
-              ]
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
@@ -2074,18 +1827,7 @@ f.event={add:function(a,c,d,e,g){var h,i,j,k,l,m,n,o,p,q,r,s;if(!(a.nodeType===3
             "pageTitle": "vault/GetCreditCard",
             "title": "GetCreditCard"
           },
-          "depth": 2,
-          "outline": [
-            {
-              "type": "heading",
-              "data": {
-                "level": 1,
-                "title": "Get Credit Card Sample",
-                "slug": "get-credit-card-sample"
-              },
-              "depth": 1
-            }
-          ]
+          "depth": 2
         }, {
           "type": "file",
           "data": {
diff --git a/sample/doc/invoice/CreateInvoice.html b/sample/doc/invoice/CreateInvoice.html
index 790abf6..4329dd0 100644
--- a/sample/doc/invoice/CreateInvoice.html
+++ b/sample/doc/invoice/CreateInvoice.html
@@ -1,6 +1,7 @@
 <!DOCTYPE html><html lang="en"><head><title>invoice/CreateInvoice</title></head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0"><meta name="groc-relative-root" content="../"><meta name="groc-document-path" content="invoice/CreateInvoice"><meta name="groc-project-path" content="invoice/CreateInvoice.php"><link rel="stylesheet" type="text/css" media="all" href="../assets/style.css"><script type="text/javascript" src="../assets/behavior.js"></script><body><div id="meta"><div class="file-path">invoice/CreateInvoice.php</div></div><div id="document"><div class="segment"><div class="code"><div class="wrapper"><span class="hljs-preprocessor">&lt;?php</span></div></div></div><div class="segment"><div class="comments "><div class="wrapper"><h1 id="create-invoice-sample">Create Invoice Sample</h1>
 <p>This sample code demonstrate how you can create
 an invoice.</p></div></div><div class="code"><div class="wrapper"><span class="hljs-keyword">require</span> <span class="hljs-keyword">__DIR__</span> . <span class="hljs-string">'/../bootstrap.php'</span>;
+<span class="hljs-keyword">use</span> <span class="hljs-title">PayPal</span>\<span class="hljs-title">Api</span>\<span class="hljs-title">Cost</span>;
 <span class="hljs-keyword">use</span> <span class="hljs-title">PayPal</span>\<span class="hljs-title">Api</span>\<span class="hljs-title">Invoice</span>;
 <span class="hljs-keyword">use</span> <span class="hljs-title">PayPal</span>\<span class="hljs-title">Api</span>\<span class="hljs-title">MerchantInfo</span>;
 <span class="hljs-keyword">use</span> <span class="hljs-title">PayPal</span>\<span class="hljs-title">Api</span>\<span class="hljs-title">BillingInfo</span>;
@@ -65,10 +66,12 @@ detailed breakdown of invoice</p></div></div><div class="code"><div class="wrapp
     -&gt;setValue(<span class="hljs-number">5</span>);</div></div></div><div class="segment"><div class="comments "><div class="wrapper"><h4 id="tax-item">Tax Item</h4>
 <p>You could provide Tax information to each item.</p></div></div><div class="code"><div class="wrapper"><span class="hljs-variable">$tax</span> = <span class="hljs-keyword">new</span> \PayPal\Api\Tax();
 <span class="hljs-variable">$tax</span>-&gt;setPercent(<span class="hljs-number">1</span>)-&gt;setName(<span class="hljs-string">"Local Tax on Sutures"</span>);
-<span class="hljs-variable">$items</span>[<span class="hljs-number">0</span>]-&gt;setTax(<span class="hljs-variable">$tax</span>);</div></div></div><div class="segment"><div class="comments "><div class="wrapper"><p>Second Item</p></div></div><div class="code"><div class="wrapper"><span class="hljs-variable">$items</span>[<span class="hljs-number">1</span>] = <span class="hljs-keyword">new</span> InvoiceItem();
+<span class="hljs-variable">$items</span>[<span class="hljs-number">0</span>]-&gt;setTax(<span class="hljs-variable">$tax</span>);</div></div></div><div class="segment"><div class="comments "><div class="wrapper"><p>Second Item</p></div></div><div class="code"><div class="wrapper"><span class="hljs-variable">$items</span>[<span class="hljs-number">1</span>] = <span class="hljs-keyword">new</span> InvoiceItem();</div></div></div><div class="segment"><div class="comments "><div class="wrapper"><p>Lets add some discount to this item.</p></div></div><div class="code"><div class="wrapper"><span class="hljs-variable">$item1discount</span> = <span class="hljs-keyword">new</span> Cost();
+<span class="hljs-variable">$item1discount</span>-&gt;setPercent(<span class="hljs-string">"3"</span>);
 <span class="hljs-variable">$items</span>[<span class="hljs-number">1</span>]
     -&gt;setName(<span class="hljs-string">"Injection"</span>)
     -&gt;setQuantity(<span class="hljs-number">5</span>)
+    -&gt;setDiscount(<span class="hljs-variable">$item1discount</span>)
     -&gt;setUnitPrice(<span class="hljs-keyword">new</span> Currency());
 
 <span class="hljs-variable">$items</span>[<span class="hljs-number">1</span>]-&gt;getUnitPrice()
@@ -78,7 +81,10 @@ detailed breakdown of invoice</p></div></div><div class="code"><div class="wrapp
 <span class="hljs-variable">$tax2</span>-&gt;setPercent(<span class="hljs-number">3</span>)-&gt;setName(<span class="hljs-string">"Local Tax on Injection"</span>);
 <span class="hljs-variable">$items</span>[<span class="hljs-number">1</span>]-&gt;setTax(<span class="hljs-variable">$tax2</span>);
 
-<span class="hljs-variable">$invoice</span>-&gt;setItems(<span class="hljs-variable">$items</span>);
+<span class="hljs-variable">$invoice</span>-&gt;setItems(<span class="hljs-variable">$items</span>);</div></div></div><div class="segment"><div class="comments "><div class="wrapper"><h4 id="final-discount">Final Discount</h4>
+<p>You can add final discount to the invoice as shown below. You could either use &quot;percent&quot; or &quot;value&quot; when providing the discount</p></div></div><div class="code"><div class="wrapper"><span class="hljs-variable">$cost</span> = <span class="hljs-keyword">new</span> Cost();
+<span class="hljs-variable">$cost</span>-&gt;setPercent(<span class="hljs-string">"2"</span>);
+<span class="hljs-variable">$invoice</span>-&gt;setDiscount(<span class="hljs-variable">$cost</span>);
 
 <span class="hljs-variable">$invoice</span>-&gt;getPaymentTerm()
     -&gt;setTermType(<span class="hljs-string">"NET_45"</span>);</div></div></div><div class="segment"><div class="comments "><div class="wrapper"><h3 id="shipping-information">Shipping Information</h3></div></div></div><div class="segment"><div class="code"><div class="wrapper"><span class="hljs-variable">$invoice</span>-&gt;getShippingInfo()
diff --git a/sample/invoice/CreateInvoice.php b/sample/invoice/CreateInvoice.php
index 3deba88..7f39064 100644
--- a/sample/invoice/CreateInvoice.php
+++ b/sample/invoice/CreateInvoice.php
@@ -5,6 +5,7 @@
 // an invoice.
 
 require __DIR__ . '/../bootstrap.php';
+use PayPal\Api\Cost;
 use PayPal\Api\Invoice;
 use PayPal\Api\MerchantInfo;
 use PayPal\Api\BillingInfo;
@@ -91,9 +92,13 @@ $items[0]->setTax($tax);
 
 // Second Item
 $items[1] = new InvoiceItem();
+// Lets add some discount to this item.
+$item1discount = new Cost();
+$item1discount->setPercent("3");
 $items[1]
     ->setName("Injection")
     ->setQuantity(5)
+    ->setDiscount($item1discount)
     ->setUnitPrice(new Currency());
 
 $items[1]->getUnitPrice()
@@ -108,6 +113,12 @@ $items[1]->setTax($tax2);
 
 $invoice->setItems($items);
 
+// #### Final Discount
+// You can add final discount to the invoice as shown below. You could either use "percent" or "value" when providing the discount
+$cost = new Cost();
+$cost->setPercent("2");
+$invoice->setDiscount($cost);
+
 $invoice->getPaymentTerm()
     ->setTermType("NET_45");