diff --git a/src/main/java/Model/TransactionCalculator.java b/src/main/java/Model/TransactionCalculator.java
index 560992d..73fe750 100644
--- a/src/main/java/Model/TransactionCalculator.java
+++ b/src/main/java/Model/TransactionCalculator.java
@@ -1,11 +1,19 @@
 package Model;
+
 import java.math.BigDecimal;
 
+/**
+ * TransactionCalculator class.
+ */
 public interface TransactionCalculator {
-    // Methods in interface is automatically public abstract.
-    BigDecimal calculateGross();
-    BigDecimal calculateCommission();
-    BigDecimal calculateTax();
-    BigDecimal calculateTotal();
+  // Methods in interface is automatically public abstract.
+  BigDecimal calculateGross();
+
+  BigDecimal calculateCommission();
+
+  BigDecimal calculateTax();
+
+  BigDecimal calculateTotal();
+
 }