diff --git a/src/main/java/edu/ntnu/idi/idatt2003/g40/mappe/SaleCalculator.java b/src/main/java/edu/ntnu/idi/idatt2003/g40/mappe/SaleCalculator.java
index b9736fd..ecc4242 100644
--- a/src/main/java/edu/ntnu/idi/idatt2003/g40/mappe/SaleCalculator.java
+++ b/src/main/java/edu/ntnu/idi/idatt2003/g40/mappe/SaleCalculator.java
@@ -2,31 +2,57 @@
 
 import java.math.BigDecimal;
 
+/**
+ * Calculator for sale transactions.
+ * <p>
+ * Calculates gross value, commission, tax and total sale value
+ * based on the share's purchase price, current sales price and quantity.
+ * </p>
+ */
 public class SaleCalculator implements TransactionCalculator {
 
-    private static final BigDecimal COMMISSION_RATE = new BigDecimal("0.01");
-    private static final BigDecimal TAX_RATE = new BigDecimal("0.30");
+    private static final BigDecimal COMMISSION_RATE = new BigDecimal("0.01"); // 1%
+    private static final BigDecimal TAX_RATE = new BigDecimal("0.30");        // 30%
 
     private final BigDecimal purchasePrice;
     private final BigDecimal salesPrice;
     private final BigDecimal quantity;
 
+    /**
+     * Creates a new {@code SaleCalculator} based on a share.
+     *
+     * @param share the share to base calculations on
+     */
     public SaleCalculator(Share share) {
         this.purchasePrice = share.getPurchasePrice();
         this.salesPrice = share.getStock().getSalesPrice();
         this.quantity = share.getQuantity();
     }
 
+    /**
+     * {@inheritDoc}
+     * Gross value = salesPrice * quantity.
+     */
     @Override
     public BigDecimal calculateGross() {
         return salesPrice.multiply(quantity);
     }
 
+    /**
+     * {@inheritDoc}
+     * Commission = 1% of gross value.
+     */
     @Override
     public BigDecimal calculateCommission() {
         return calculateGross().multiply(COMMISSION_RATE);
     }
 
+    /**
+     * {@inheritDoc}
+     * Tax = 30% of profit.
+     * Profit = gross - commission - (purchasePrice * quantity).
+     * If profit is negative or zero, tax is zero.
+     */
     @Override
     public BigDecimal calculateTax() {
         BigDecimal purchaseCost = purchasePrice.multiply(quantity);
@@ -39,6 +65,10 @@ public BigDecimal calculateTax() {
                 : BigDecimal.ZERO;
     }
 
+    /**
+     * {@inheritDoc}
+     * Total value = gross - commission - tax.
+     */
     @Override
     public BigDecimal calculateTotal() {
         return calculateGross()