diff --git a/mainfile.cpp b/mainfile.cpp
index 18ea8ea..66a973c 100644
--- a/mainfile.cpp
+++ b/mainfile.cpp
@@ -4,6 +4,7 @@
 #include<conio.h>
 #include"productlib.h"
 #include"billlib.h"
+#include"invoicelib.h"
 #include<time.h>
 using namespace std;