diff --git a/qr_code_crypto/src/lib.rs b/qr_code_crypto/src/lib.rs
index bb89276..5de21c4 100644
--- a/qr_code_crypto/src/lib.rs
+++ b/qr_code_crypto/src/lib.rs
@@ -1,3 +1,5 @@
+use rust_decimal::prelude::*;
+
 pub trait CryptoInvoice {
     fn new(address: &str) -> Self;
     fn set_query_part(self, name: &str, value: &str) -> Self;
@@ -43,3 +45,9 @@ impl CryptoInvoice for MoneroInvoice {
         format!("monero:{}{}", self.address, self.query)
     }
 }
+
+impl MoneroInvoice {
+    pub fn add_amount(self, amount: Decimal) -> Self {
+        self.set_query_part("tx_amount", &amount.to_string())
+    }
+}
diff --git a/qr_code_crypto/src/main.rs b/qr_code_crypto/src/main.rs
index c9132fd..0ca4c5f 100644
--- a/qr_code_crypto/src/main.rs
+++ b/qr_code_crypto/src/main.rs
@@ -16,6 +16,7 @@ fn create_and_print_qr_invoice(invoice: impl CryptoInvoice) {
 
 fn main() {
     let monero_donation_adress = "888tNkZrPN6JsEgekjMnABU4TBzc2Dt29EPAvkRxbANsAnjyPbb3iQ1YBRk1UXcdRsiKc9dhwMVgN5S9cQUiyoogDavup3H".to_string();
-    let monero_invoice = MoneroInvoice::new(&monero_donation_adress);
+    let monero_invoice =
+        MoneroInvoice::new(&monero_donation_adress).add_amount(Decimal::new(200, 2));
     create_and_print_qr_invoice(monero_invoice);
 }