Bank: Have your bank statements with returned cheques available. Have your cheque book with cheque stubs handy.
Sales Invoices: Keep the "paid" invoices separate from the "Unpaid" invoices. On paid invoices indicate - date deposited, cheque number and amount if not fully paid.
Bills: Keep the "Paid" invoices separate from the "Unpaid" invoices. Indicate on the invoice the amount if not fully paid and the reason for the short payment. Document on the invoice the date of payment and the method of payment.
Receipts: Indicate on receipt what it is for. If it involves meals, indicate who it was for. Keep personal expenditures separate from business expenditures.
Tip: As best as possible, maintain separate bank accounts for personal and business use.
Backup: Always backup your computerized data after each use. It is best to backup to an external site.