Do I need to handle income transactions that are allocated to sales invoices sent from the system?

When you send a sales invoice from Solo, the payment is automatically allocated to the invoice if the customer uses the right bank reference code. In other words, you do not have to allocate income transactions to sales invoices sent from the program.

If the customer uses a wrong bank reference code, you can allocate the income manually by clicking Add to invoice > Add to sales invoice. Read the detailed instructions here.