Private Sub PrintInvoice() Dim printDoc As New Printing.PrintDocument() AddHandler printDoc.PrintPage, AddressOf PrintPageHandler Dim printDialog1 As New PrintDialog() printDialog1.Document = printDoc If printDialog1.ShowDialog() = DialogResult.OK Then printDoc.Print() End If End Sub Private Sub PrintPageHandler(sender As Object, e As Printing.PrintPageEventArgs) Dim yPos As Single = e.MarginBounds.Top Dim leftMargin As Single = e.MarginBounds.Left Dim font As New Font("Arial", 12) Dim largeFont As New Font("Arial", 16, FontStyle.Bold)

'Header e.Graphics.DrawString("ABC Electronics", largeFont, Brushes.Black, leftMargin, yPos) yPos += 30 e.Graphics.DrawString("Invoice #: " & lblInvoiceNo.Text, font, Brushes.Black, leftMargin, yPos) yPos += 20 e.Graphics.DrawString("Date: " & DateTime.Now.ToShortDateString(), font, Brushes.Black, leftMargin, yPos) yPos += 30 e.Graphics.DrawString("Items:", font, Brushes.Black, leftMargin, yPos) yPos += 20

Private Sub SaveInvoice() Using conn As SqlConnection = getConnection() conn.Open() Dim transaction As SqlTransaction = conn.BeginTransaction() Try '1. Insert into tbl_Invoice_Master Dim masterQuery As String = "INSERT INTO tbl_Invoice_Master (InvoiceDate, CustomerID, SubTotal, TaxAmount, GrandTotal) " & "VALUES (@date, @custID, @sub, @tax, @grand); SELECT SCOPE_IDENTITY();" Dim newInvoiceNo As Integer = 0 Using cmdMaster As New SqlCommand(masterQuery, conn, transaction) cmdMaster.Parameters.AddWithValue("@date", DateTime.Now) cmdMaster.Parameters.AddWithValue("@custID", GetCurrentCustomerID()) 'Function to get selected customer ID cmdMaster.Parameters.AddWithValue("@sub", lblSubTotal.Text) cmdMaster.Parameters.AddWithValue("@tax", lblTax.Text) cmdMaster.Parameters.AddWithValue("@grand", lblGrandTotal.Text) newInvoiceNo = Convert.ToInt32(cmdMaster.ExecuteScalar()) End Using '2. Insert into tbl_Invoice_Details for each row in cart Dim detailsQuery As String = "INSERT INTO tbl_Invoice_Details (InvoiceNo, ProductID, Quantity, Rate, Total) " & "VALUES (@invNo, @prodID, @qty, @rate, @total)" For Each row As DataGridViewRow In dgvCart.Rows Using cmdDetails As New SqlCommand(detailsQuery, conn, transaction) cmdDetails.Parameters.AddWithValue("@invNo", newInvoiceNo) cmdDetails.Parameters.AddWithValue("@prodID", row.Cells("ProductID").Value) cmdDetails.Parameters.AddWithValue("@qty", row.Cells("Quantity").Value) cmdDetails.Parameters.AddWithValue("@rate", row.Cells("Rate").Value) cmdDetails.Parameters.AddWithValue("@total", row.Cells("Total").Value) cmdDetails.ExecuteNonQuery() '3. Update stock in tbl_Products Dim stockQuery As String = "UPDATE tbl_Products SET StockQuantity = StockQuantity - @qty WHERE ProductID = @prodID" Using cmdStock As New SqlCommand(stockQuery, conn, transaction) cmdStock.Parameters.AddWithValue("@qty", row.Cells("Quantity").Value) cmdStock.Parameters.AddWithValue("@prodID", row.Cells("ProductID").Value) cmdStock.ExecuteNonQuery() End Using End Using Next transaction.Commit() MessageBox.Show("Invoice saved successfully. Invoice No: " & newInvoiceNo) ClearCart() Catch ex As Exception transaction.Rollback() MessageBox.Show("Failed to save invoice: " & ex.Message) End Try End Using End Sub The final piece is printing. Using the PrintDocument component from the toolbox:

If you are a small retail shop with unique workflows (e.g., laundry billing, restaurant split-bill), VB.NET source code gives you freedom . If you need a standard retail POS, buy ready-made software. Conclusion The "vb.net billing software source code" is not just a collection of files; it is a blueprint for understanding transactional systems, database integrity, and UI/UX in desktop applications. By mastering the code patterns shown above—database transactions, DataGridView cart management, and dynamic printing—you can build a billing system that rivals commercial products.

Private Sub CalculateTotal() Dim subTotal As Decimal = 0 For Each row As DataGridViewRow In dgvCart.Rows subTotal += Convert.ToDecimal(row.Cells("Total").Value) Next

Whether you are a student completing a final-year project or a small business owner tired of expensive software, VB.NET empowers you to take control. Start with the core modules, iterate with features like GST reporting or customer credit limits, and you will have a professional application ready for deployment.

Imports System.Data.SqlClient Module mod_DB Public connString As String = "Data Source=localhost\SQLEXPRESS;Initial Catalog=BillingDB;Integrated Security=True"