Invoicing is an important part of any small business. These formal transaction documents help both you and your customers. Sending invoices to customers helps them keep track of their expenses, claim sales tax credits like VAT or GST and ensures that your small business gets paid correctly and on time.
For your small business processes, invoices are a part of record-keeping so that you can properly track cash flow and reconcile income.  Having clear records of your sales and transactions helps your small business decision-making as well as financial reporting and tax obligations.