diff --git a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
index 56fe02359..6948c890b 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
@@ -1,30 +1,76 @@
 package pl.edu.agh.mwo.invoice;
 
 import java.math.BigDecimal;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
 
 import pl.edu.agh.mwo.invoice.product.Product;
 
 public class Invoice {
     private Collection<Product> products;
 
+    public Invoice() {
+        this.products = new ArrayList<>();
+    }
+
+
     public void addProduct(Product product) {
-        // TODO: implement
+        this.addProduct(product,1);
     }
 
+
     public void addProduct(Product product, Integer quantity) {
-        // TODO: implement
+        if(product == null) {
+            throw new IllegalArgumentException("Product cannot be null");
+
+        } if (quantity <= 0) {
+            throw new IllegalArgumentException("Quantity must be greater than 0");
+        }
+
+        this.productsMap.put(product,quantity);
     }
 
-    public BigDecimal getSubtotal() {
-        return null;
+
+    private Map<Product,Integer> productsMap = new HashMap<>();
+
+    public BigDecimal getNetValue() {
+
+
+        BigDecimal netValue = BigDecimal.ZERO;
+
+        for (Product product : this.productsMap.keySet()) {
+            Integer quantity = this.productsMap.get(product);
+            BigDecimal price = product.getPrice();
+            price = price.multiply(BigDecimal.valueOf(quantity));
+            netValue = netValue.add(price);
+
+        }return netValue;
+
+
     }
 
+
     public BigDecimal getTax() {
-        return null;
+        return getGrossValue().subtract(getNetValue());
     }
 
-    public BigDecimal getTotal() {
-        return null;
+
+    public BigDecimal getGrossValue() {
+        BigDecimal netValue = BigDecimal.ZERO;
+
+        for (Product product : this.productsMap.keySet()) {
+            Integer quantity = this.productsMap.get(product);
+            BigDecimal price = product.getPriceWithTax();
+            price = price.multiply(BigDecimal.valueOf(quantity));
+            netValue = netValue.add(price);
+
+        }
+        return netValue;
+
     }
+
+
 }
+
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/product/OtherProduct.java b/src/main/java/pl/edu/agh/mwo/invoice/product/OtherProduct.java
index e324fe5a4..be62a994b 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/product/OtherProduct.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/product/OtherProduct.java
@@ -3,6 +3,7 @@
 import java.math.BigDecimal;
 
 public class OtherProduct extends Product {
+
     public OtherProduct(String name, BigDecimal price) {
         super(name, price, new BigDecimal("0.23"));
     }
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java b/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
index 318de9ac9..dc09e2fb7 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
@@ -9,25 +9,41 @@ public abstract class Product {
 
     private final BigDecimal taxPercent;
 
+
     protected Product(String name, BigDecimal price, BigDecimal tax) {
+
+        if(name == null || name.isBlank()) {
+            throw new IllegalArgumentException("Product name cannot be null");
+        }
         this.name = name;
+
+        if(price == null) {
+            throw new IllegalArgumentException("Price cannot be null");
+        }
         this.price = price;
+
+       if(tax == null|| price.compareTo(BigDecimal.ZERO) < 0) {
+           throw new IllegalArgumentException("Tax percent cannot be null");
+       }
         this.taxPercent = tax;
     }
 
+
     public String getName() {
-        return null;
+        return this.name;
     }
 
     public BigDecimal getPrice() {
-        return null;
+        return this.price;
     }
 
     public BigDecimal getTaxPercent() {
-        return null;
+        return this.taxPercent;
     }
 
     public BigDecimal getPriceWithTax() {
-        return null;
+        BigDecimal result = this.price.multiply(this.taxPercent);
+        return (BigDecimal)price.add(result);
+
     }
 }
diff --git a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
index 7f4b6f795..44696ebc5 100644
--- a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
+++ b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
@@ -7,7 +7,6 @@
 import org.junit.Before;
 import org.junit.Test;
 
-import pl.edu.agh.mwo.invoice.Invoice;
 import pl.edu.agh.mwo.invoice.product.DairyProduct;
 import pl.edu.agh.mwo.invoice.product.OtherProduct;
 import pl.edu.agh.mwo.invoice.product.Product;
@@ -21,9 +20,10 @@ public void createEmptyInvoiceForTheTest() {
         invoice = new Invoice();
     }
 
+
     @Test
     public void testEmptyInvoiceHasEmptySubtotal() {
-        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getNetValue()));
     }
 
     @Test
@@ -33,30 +33,30 @@ public void testEmptyInvoiceHasEmptyTaxAmount() {
 
     @Test
     public void testEmptyInvoiceHasEmptyTotal() {
-        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getTotal()));
+        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getGrossValue()));
     }
 
     @Test
-    public void testInvoiceSubtotalWithTwoDifferentProducts() {
-        Product onions = new TaxFreeProduct("Warzywa", new BigDecimal("10"));
+    public void testInvoiceNetValueWithTwoDifferentProducts() {
+        Product onions = new TaxFreeProduct("WarzywaWazrywa", new BigDecimal("10"));
         Product apples = new TaxFreeProduct("Owoce", new BigDecimal("10"));
         invoice.addProduct(onions);
         invoice.addProduct(apples);
-        Assert.assertThat(new BigDecimal("20"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(new BigDecimal("20"), Matchers.comparesEqualTo(invoice.getNetValue()));
     }
 
     @Test
-    public void testInvoiceSubtotalWithManySameProducts() {
+    public void testInvoiceSNetValueWithManySameProducts() {
         Product onions = new TaxFreeProduct("Warzywa", BigDecimal.valueOf(10));
         invoice.addProduct(onions, 100);
-        Assert.assertThat(new BigDecimal("1000"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(new BigDecimal("1000"), Matchers.comparesEqualTo(invoice.getNetValue()));
     }
 
     @Test
     public void testInvoiceHasTheSameSubtotalAndTotalIfTaxIsZero() {
         Product taxFreeProduct = new TaxFreeProduct("Warzywa", new BigDecimal("199.99"));
         invoice.addProduct(taxFreeProduct);
-        Assert.assertThat(invoice.getTotal(), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(invoice.getGrossValue(), Matchers.comparesEqualTo(invoice.getNetValue()));
     }
 
     @Test
@@ -64,7 +64,7 @@ public void testInvoiceHasProperSubtotalForManyProducts() {
         invoice.addProduct(new TaxFreeProduct("Owoce", new BigDecimal("200")));
         invoice.addProduct(new DairyProduct("Maslanka", new BigDecimal("100")));
         invoice.addProduct(new OtherProduct("Wino", new BigDecimal("10")));
-        Assert.assertThat(new BigDecimal("310"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(new BigDecimal("310"), Matchers.comparesEqualTo(invoice.getNetValue()));
     }
 
     @Test
@@ -86,7 +86,7 @@ public void testInvoiceHasProperTotalValueForManyProduct() {
         invoice.addProduct(new DairyProduct("Maslo", new BigDecimal("100")));
         // price with tax: 12.30
         invoice.addProduct(new OtherProduct("Chipsy", new BigDecimal("10")));
-        Assert.assertThat(new BigDecimal("320.30"), Matchers.comparesEqualTo(invoice.getTotal()));
+        Assert.assertThat(new BigDecimal("320.30"), Matchers.comparesEqualTo(invoice.getGrossValue()));
     }
 
     @Test
@@ -97,7 +97,7 @@ public void testInvoiceHasPropoerSubtotalWithQuantityMoreThanOne() {
         invoice.addProduct(new DairyProduct("Kozi Serek", new BigDecimal("10")), 3);
         // 1000x pinezka - price: 10
         invoice.addProduct(new OtherProduct("Pinezka", new BigDecimal("0.01")), 1000);
-        Assert.assertThat(new BigDecimal("50"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(new BigDecimal("50"), Matchers.comparesEqualTo(invoice.getNetValue()));
     }
 
     @Test
@@ -108,7 +108,7 @@ public void testInvoiceHasPropoerTotalWithQuantityMoreThanOne() {
         invoice.addProduct(new DairyProduct("Chedar", new BigDecimal("10")), 3);
         // 1000x pinezka - price with tax: 12.30
         invoice.addProduct(new OtherProduct("Pinezka", new BigDecimal("0.01")), 1000);
-        Assert.assertThat(new BigDecimal("54.70"), Matchers.comparesEqualTo(invoice.getTotal()));
+        Assert.assertThat(new BigDecimal("54.70"), Matchers.comparesEqualTo(invoice.getGrossValue()));
     }
 
     @Test(expected = IllegalArgumentException.class)