You need to add at least one customer before creating invoices. Use Customers–Add Customer to add new customers.

To change existing customers, first you list them using Customers–Reports–Search. Customers are listed with hyperlinks to edit each customer.

Sales invoices are created using AR–Sales Invoice menu option. The only mandatory columns are Customer and Invoice Date. Rest of the columns can be left blank.

Once you enter an item (part, service) and click 'Update', a new line opens. This way you can enter any number of items (parts, services etc.) in the detail portion of the invoice.

AR–Add Transaction menu option is used to create AR Transactions. These transactions allow you to record your sales in correct GL accounts without creating an invoice.

You can record cash receipts from customer while creating invoices (for cash sales) or afterward using Cash–Receipt menu option.