A book-keeper can submit a clients tax return. You will need to register as an agent with HM Revenue & Customs/goverment gateway. You will need a 64-8 for each client. If you are a member with ICB you should take the self assessment exam before offering tax return service.
An accountant would usually expect books upto trial balance stage. If using eg sage I would usually give the accountant a backup on a USB pen. They may not require printed reports, depends on the accountant.