diff --git a/Cargo.toml b/Cargo.toml
index 2639b89..fed64fd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,14 +14,14 @@ edition = "2018"
 
 [dependencies]
 reqwest = { version = "0.11.0", features = ["json"] }
-serde = { version = "1.0.118", features = ["derive"] }
+serde = { version = "1.0.119", features = ["derive"] }
 serde_json = "1.0.61"
 serde_with = "1.6.2"
 chrono = { version = "0.4.19", features = ["serde"] }
 jsonwebtoken = "7.2.0"
 base64 = "0.13.0"
-log = "0.4.11"
-bytes = "1.0.0"
+log = "0.4.13"
+bytes = "1.0.1"
 
 [dev-dependencies]
 tokio = { version = "1.0.1", features = ["macros", "rt-multi-thread"] }
diff --git a/examples/invoice.rs b/examples/invoice.rs
new file mode 100644
index 0000000..2c2ae71
--- /dev/null
+++ b/examples/invoice.rs
@@ -0,0 +1,81 @@
+use paypal_rs::{
+    Client,
+    HeaderParams,
+    Prefer,
+    invoice::*,
+    common::*,
+    errors::*,
+};
+
+#[tokio::main]
+async fn main() -> Result<(), ResponseError> {
+    dotenv::dotenv().ok();
+
+    let clientid = std::env::var("PAYPAL_CLIENTID").unwrap();
+    let secret = std::env::var("PAYPAL_SECRET").unwrap();
+
+    let mut client = Client::new(clientid, secret, true);
+
+    let payload = InvoicePayload {
+        detail: InvoiceDetail {
+            currency_code: Currency::EUR,
+            //reference: Some("deal-ref".to_owned()),
+            ..Default::default()
+        },
+        invoicer: Some(InvoicerInfo {
+            name: Some(Name {
+                given_name: Some("Lucas".to_owned()),
+                prefix: None,
+                suffix: None,
+                surname: None,
+                full_name: None,
+                middle_name: None,
+                alternate_full_name: None,
+            }),
+            phones: None,
+            tax_id: None,
+            website: None,
+            business_name: "Lucas Corp".to_owned(),
+            logo_url: None,
+            // needs to be a valid address...
+            email_address: Some("merchant@example.com".to_owned()),
+            additional_notes: None,
+        }),
+        items: vec![
+            Item {
+                id: None,
+                name: "My item".to_owned(),
+                unit_amount: Money {
+                    currency_code: Currency::EUR,
+                    value: "10.0".to_owned()
+                },
+                quantity: "1".to_owned(),
+                discount: None,
+                item_date: None,
+                description: Some("A random item".to_owned()),
+                tax: Some(Tax {
+                    name: "Sales tax".to_owned(),
+                    percent: "7".to_owned(),
+                    amount: None,
+                }),
+                unit_of_measure: Some(UnitOfMeasure::Quantity),
+            }
+        ],
+        ..Default::default()
+    };
+    match client.create_draft_invoice(payload, HeaderParams::default()).await {
+        Ok(r) => {
+            println!("{:#?}", r);
+        },
+        Err(ResponseError::HttpError(e)) => {
+            println!("{}", e);
+        },
+        Err(e) => {
+            println!("{:#?}", e);
+        }
+    }
+
+    // some stuff is not sent when representation is minimal.
+
+    Ok(())
+}
diff --git a/src/common.rs b/src/common.rs
index 72b92d5..a485802 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -94,7 +94,7 @@ pub struct LinkDescription {
     /// The complete target URL.
     pub href: String,
     /// The link relation type, which serves as an ID for a link that unambiguously describes the semantics of the link.
-    pub rel: String,
+    pub rel: Option<String>,
     /// The HTTP method required to make the related call.
     pub method: Option<LinkMethod>,
 }
diff --git a/src/errors.rs b/src/errors.rs
index cfb1523..dd9ba98 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -11,9 +11,9 @@ pub struct PaypalError {
     /// The error name.
     pub name: String,
     /// The error message.
-    pub message: String,
+    pub message: Option<String>,
     /// Paypal debug id
-    pub debug_id: String,
+    pub debug_id: Option<String>,
     /// Error details
     pub details: Vec<HashMap<String, String>>,
     /// Only available on Identity errors
diff --git a/src/invoice.rs b/src/invoice.rs
index 244a3a3..3bf24de 100644
--- a/src/invoice.rs
+++ b/src/invoice.rs
@@ -113,7 +113,7 @@ pub struct InvoiceDetail {
     /// The reference data. Includes a post office (PO) number.
     pub reference: Option<String>,
     /// The three-character ISO-4217 currency code that identifies the currency.
-    pub currency_code: String,
+    pub currency_code: Currency,
     /// A note to the invoice recipient. Also appears on the invoice notification email.
     pub note: Option<String>,
     /// The general terms of the invoice. Can include return or cancellation policy and other terms and conditions.
@@ -123,13 +123,13 @@ pub struct InvoiceDetail {
     /// An array of PayPal IDs for the files that are attached to an invoice.
     pub attachments: Option<Vec<FileReference>>,
     /// The invoice number. Default is the number that is auto-incremented number from the last number.
-    pub invoice_number: String,
+    pub invoice_number: Option<String>,
     /// The invoice date as specificed by the sender
-    pub invoice_date: chrono::NaiveDate,
+    pub invoice_date: Option<chrono::DateTime<chrono::Utc>>,
     /// The payment due date for the invoice.
     pub payment_term: Option<PaymentTerm>,
     /// The audit metadata
-    pub metadata: Metadata,
+    pub metadata: Option<Metadata>,
 }
 
 /// A name to be used as recipient, etc.
@@ -258,7 +258,7 @@ pub struct Discount {
 /// The unit of measure for the invoiced item.
 #[derive(Debug, Serialize, Deserialize, Eq, PartialEq)]
 #[serde(rename_all = "SCREAMING_SNAKE_CASE")]
-pub enum UnitOffMeasure {
+pub enum UnitOfMeasure {
     /// The unit of measure is quantity. This invoice template is typically used for physical goods.
     Quantity,
     /// The unit of measure is hours. This invoice template is typically used for services.
@@ -289,7 +289,7 @@ pub struct Item {
     /// Discount as a percent or amount at invoice level. The invoice discount amount is subtracted from the item total.
     pub discount: Option<Discount>,
     /// The unit of measure for the invoiced item. For AMOUNT the unit_amount and quantity are not shown on the invoice.
-    pub unit_of_measure: Option<UnitOffMeasure>,
+    pub unit_of_measure: Option<UnitOfMeasure>,
 }
 
 /// The partial payment details.
@@ -369,7 +369,7 @@ pub struct Breakdown {
 #[derive(Debug, Default, Serialize, Deserialize)]
 pub struct Amount {
     /// The [three-character ISO-4217 currency code](https://developer.paypal.com/docs/integration/direct/rest/currency-codes/) that identifies the currency.
-    pub currency_code: String,
+    pub currency_code: Currency,
     /// The value, which might be:
     /// - An integer for currencies like JPY that are not typically fractional.
     /// - A decimal fraction for currencies like TND that are subdivided into thousandths.
@@ -382,9 +382,9 @@ pub struct Amount {
 
 impl Amount {
     /// Creates a new amount with the required values.
-    pub fn new<S: Into<String>>(currency_code: S, value: S) -> Self {
+    pub fn new(currency_code: Currency, value: &str) -> Self {
         Amount {
-            currency_code: currency_code.into(),
+            currency_code,
             value: value.into(),
             breakdown: None,
         }
@@ -690,8 +690,9 @@ impl super::Client {
         let res = build.json(&invoice).send().await?;
 
         if res.status().is_success() {
-            let x = res.json::<Invoice>().await?;
-            Ok(x)
+            println!("{:#?}", res.text().await?);
+            //let x = res.json::<Invoice>().await?;
+            Ok(())
         } else {
             Err(res.json::<PaypalError>().await?.into())
         }
@@ -911,4 +912,5 @@ mod tests {
 
         println!("{:?}", list);
     }
-}
\ No newline at end of file
+}
+