The best report is under Payments->Report Repository

A Transaction report will be by order in a CSV spreadsheet. Summary report will be a PDF. I would guess your accountant would want the CSV transaction report but best to ask them.

If you are using VAT Calculation services and have set your product types correctly then VAT will be calculated for you in the above reports.

You will also need to send them all the tax invoices from your Tax Document Library so they can claim back money on fees.

That would cover sales and fees on Amazon you just then need to provide invoices/sales for purchases and non Amazon sales.

Ask you accountant as well, if they have other Amazon Clients they may have a list of information they require from you. If they don't have other Amazon Clients be a little aware of using them as some accountants struggle to get their head around Amazon.