I have recently started to use QuickFile for a scout centre I volunteer at. We process hand written booking forms and use these to generate a client account from which we invoice for courses that we run.
Is it possible for invoices to show the clients email address and phone number?
Yes, I would also appreciate at least phone number on invoices, too - simply because we use invoices as a job descriptions, too - so for staff leaving office with printed invoice (= work description) is very handy to have a phone number if they will need to contact the customer.
As LPMM says above, it would be a similar situation. I save off the invoices as they are generated to a shared box account, these are then picked up by other volunteers at our centre (volunteer staff are based across the UK). If there are any queries for a booking by any member of staff, the invoice would have all the data.