diff --git a/name.abuchen.portfolio.ui.tests/src/name/abuchen/portfolio/ui/dialogs/transactions/AbstractSecurityTransactionModelTest.java b/name.abuchen.portfolio.ui.tests/src/name/abuchen/portfolio/ui/dialogs/transactions/AbstractSecurityTransactionModelTest.java
new file mode 100644
index 0000000000..f7ec698798
--- /dev/null
+++ b/name.abuchen.portfolio.ui.tests/src/name/abuchen/portfolio/ui/dialogs/transactions/AbstractSecurityTransactionModelTest.java
@@ -0,0 +1,159 @@
+package name.abuchen.portfolio.ui.dialogs.transactions;
+
+import static org.junit.Assert.assertEquals;
+
+import java.math.BigDecimal;
+import java.text.MessageFormat;
+
+import org.eclipse.core.databinding.validation.ValidationStatus;
+import org.junit.Before;
+import org.junit.Test;
+
+import name.abuchen.portfolio.model.Client;
+import name.abuchen.portfolio.model.PortfolioTransaction;
+import name.abuchen.portfolio.model.PortfolioTransaction.Type;
+import name.abuchen.portfolio.ui.Messages;
+
+@SuppressWarnings("nls")
+public class AbstractSecurityTransactionModelTest
+{
+    private AbstractSecurityTransactionModel model;
+
+    @Before
+    public void setup()
+    {
+        Client client = new Client();
+        PortfolioTransaction.Type type = PortfolioTransaction.Type.BUY;
+
+        model = new AbstractSecurityTransactionModel(client, type)
+        {
+            @Override
+            public boolean accepts(Type type)
+            {
+                return true;
+            }
+
+            @Override
+            public void setSource(Object source)
+            {
+            }
+
+            @Override
+            public boolean hasSource()
+            {
+                return false;
+            }
+
+            @Override
+            public String getTransactionCurrencyCode()
+            {
+                return null;
+            }
+
+            @Override
+            public void applyChanges()
+            {
+            }
+        };
+    }
+
+    @Test
+    public void testCalculationStatus_WithValidData()
+    {
+        model.setShares(1);
+        model.setQuote(BigDecimal.valueOf(100));
+        model.setGrossValue(100);
+        model.setExchangeRate(BigDecimal.valueOf(0.5));
+        model.setConvertedGrossValue(200);
+        model.setTotal(800);
+        model.setFees(50);
+        model.setTaxes(100);
+        model.setForexFees(150);
+        model.setForexTaxes(200);
+
+        assertEquals(model.calculateStatus(), ValidationStatus.ok());
+
+        // 800 = 1650 - (200 / 0.5) - (150 / 0.5) - 100 - 50
+        assertEquals(800L, model.calculateConvertedGrossValue());
+
+        // 1650 = setTotal(800) + (200 / 0.5) + (150 / 0.5) + 100 + 50
+        assertEquals(1650L, model.calculateTotal());
+    }
+
+    @Test
+    public void testCalculationStatus_WithInvalidData()
+    {
+        model.setShares(0);
+        model.setQuote(BigDecimal.valueOf(0));
+        model.setGrossValue(0);
+        model.setExchangeRate(BigDecimal.valueOf(0));
+        model.setConvertedGrossValue(0);
+        model.setTotal(0);
+
+        assertEquals(model.calculateStatus(), ValidationStatus
+                        .error(MessageFormat.format(Messages.MsgDialogInputRequired, Messages.ColumnShares)));
+    }
+
+    @Test
+    public void testCalculationStatus_WithInvalidDataTotalAndSubTotal()
+    {
+        model.setShares(1);
+        model.setQuote(BigDecimal.valueOf(100));
+        model.setGrossValue(0);
+        model.setConvertedGrossValue(0);
+        model.setTotal(0);
+
+        assertEquals(model.calculateStatus(), ValidationStatus
+                        .error(MessageFormat.format(Messages.MsgDialogInputRequired, Messages.ColumnSubTotal)));
+    }
+
+    @Test
+    public void testCalculationStatus_WithInvalidDataSubTotal()
+    {
+        model.setShares(1);
+        model.setQuote(BigDecimal.valueOf(100));
+        model.setGrossValue(100);
+        model.setConvertedGrossValue(0);
+        model.setTotal(0);
+
+        assertEquals(model.calculateStatus(), ValidationStatus
+                        .error(MessageFormat.format(Messages.MsgDialogInputRequired, Messages.ColumnSubTotal)));
+    }
+
+    @Test
+    public void testCalculationStatus_WithInvalidDataQuote()
+    {
+        model.setShares(1);
+        model.setQuote(BigDecimal.valueOf(0));
+        model.setGrossValue(100);
+        model.setConvertedGrossValue(0);
+        model.setTotal(100);
+
+        assertEquals(model.calculateStatus(),
+                        ValidationStatus.error(String.format(Messages.CellEditor_NotANumber, model.getQuote())));
+    }
+
+    @Test
+    public void testCalculateStatus_WithNegativeShares()
+    {
+        model.setShares(-1);
+        model.setQuote(BigDecimal.valueOf(100));
+
+        assertEquals(model.calculateStatus(),
+                        ValidationStatus.error(String.format(Messages.CellEditor_NotANumber, model.getShares())));
+
+        assertEquals(0L, model.getTotal());
+    }
+
+    @Test
+    public void testCalculateStatus_WithNegativeQuote()
+    {
+        model.setShares(1);
+        model.setQuote(BigDecimal.valueOf(-100));
+
+        assertEquals(model.calculateStatus(),
+                        ValidationStatus.error(String.format(Messages.CellEditor_NotANumber, model.getQuote())));
+
+        assertEquals(0L, model.getTotal());
+    }
+}
diff --git a/name.abuchen.portfolio.ui/src/name/abuchen/portfolio/ui/dialogs/transactions/AbstractSecurityTransactionModel.java b/name.abuchen.portfolio.ui/src/name/abuchen/portfolio/ui/dialogs/transactions/AbstractSecurityTransactionModel.java
index dce4132a8d..5d49deef9c 100644
--- a/name.abuchen.portfolio.ui/src/name/abuchen/portfolio/ui/dialogs/transactions/AbstractSecurityTransactionModel.java
+++ b/name.abuchen.portfolio.ui/src/name/abuchen/portfolio/ui/dialogs/transactions/AbstractSecurityTransactionModel.java
@@ -196,11 +196,17 @@ public IStatus getCalculationStatus()
      * quote (2 digits currently) and the exchange rate (4 digits), the gross
      * value and converted gross value are checked against a range.
      */
-    private IStatus calculateStatus()
+    protected IStatus calculateStatus()
     {
+        if (shares < 0L)
+            return ValidationStatus.error(String.format(Messages.CellEditor_NotANumber, shares));
+
         if (shares == 0L)
             return ValidationStatus.error(MessageFormat.format(Messages.MsgDialogInputRequired, Messages.ColumnShares));
 
+        if (quote.signum() == -1)
+            return ValidationStatus.error(String.format(Messages.CellEditor_NotANumber, quote));
+
         if ((grossValue == 0L || convertedGrossValue == 0L) && type != PortfolioTransaction.Type.DELIVERY_OUTBOUND)
             return ValidationStatus
                             .error(MessageFormat.format(Messages.MsgDialogInputRequired, Messages.ColumnSubTotal));
@@ -274,7 +280,7 @@ protected void updateSharesAndQuote()
         // do not auto-suggest shares and quote when editing an existing transaction
         if (hasSource())
             return;
-        
+
         if (type == PortfolioTransaction.Type.SELL || type == PortfolioTransaction.Type.DELIVERY_OUTBOUND)
         {
             boolean hasPosition = false;
@@ -622,7 +628,7 @@ protected long calculateConvertedGrossValue()
         }
     }
 
-    private long calculateTotal()
+    protected long calculateTotal()
     {
         long feesAndTaxes = fees + taxes + Math.round(exchangeRate.doubleValue() * (forexFees + forexTaxes));