diff --git a/src/main/java/com/mycompany/mavenproject29/Mavenproject29.java b/src/main/java/com/mycompany/mavenproject29/Mavenproject29.java
index bc9e1d6..52414d4 100644
--- a/src/main/java/com/mycompany/mavenproject29/Mavenproject29.java
+++ b/src/main/java/com/mycompany/mavenproject29/Mavenproject29.java
@@ -182,13 +182,30 @@ public class Mavenproject29 {
         }
         else{
             int multiplicador = 9;
+            int soma = 0;
             for(int i = 0; i < nif.length() - 1; i++){
                 int digito = 
                         Integer.parseInt(
                                 String.valueOf(nif.charAt(i)));
                 int multiplicacao = digito * multiplicador;
+                soma += multiplicacao;
                 multiplicador--;
             }
+            int resto = soma % 11;
+            int digitoControlo;
+            if (resto == 0 || resto == 1) {
+                digitoControlo = 0;
+            }
+            else{
+                digitoControlo = 11 - resto;
+            }
+            int nonoDigito = Integer.parseInt(String.valueOf(nif.charAt(8)));
+            if(nonoDigito == digitoControlo){
+                System.out.println("Válido");
+            }
+            else{
+                System.out.println("Inválido");
+            }
         }
     
     }