I use
myHours for time tracking (free online software - saves all the back-ups!) - I can add notes and any extra costs like postage/printing/mileage etc. It is easily exported to Excel where I then add my header logo and print to PDF.
I use this as the basis to fill out invoices from my online accounting program,
Kashflow (only available in the UK I think). J can then either print to PDF or email direct to client. This system also emails me when invoices/payments (in or out) are overdue and I can also print/email client statements and late payment letters. Best thing about Kashflow is that my account can access my accounts direct and makes life so much easier if I have a problem and need to discuss with him. It is also online and saves on the back ups with all reports etc exportable to Office Suite.
I invoice main clients monthly on 14 day payment terms, and ad hoc clients at the end of the project on same terms. iIalso only bill to nearest minute (not 15 minutes as many VAs do).
Dawn