FreeAgent is a software suitable for very small businesses. According to their website:
Build professional estimates and proposals which can be tracked through to approval and converted to invoices.
Charts of invoice payments show you, month-by-month, what payments are due, overdue or have been paid.
Track what your company owes you by adding out-of-pocket expenses, including scanned expense receipts.
Reconcile money in and out of the business via your electronic bank statements and build monthly balance charts.
Visual Profit and Loss statements show you how much money your business is making and spending.
Our unique tax timeline shows you what you owe the taxman and when. Export this to your Outlook or Google calendar.