Whatever you submit you need proof of ON PAPER.
You need a copy of every invoice you issued to every customer, and also every invoice and receipt you were issued with whenever you bought something.
Your bank statement is not valid evidence.
Credit card receipts are not valid, for example it must be the additional "VAT Receipt" that you ask for in the petrol station when you fill up.
You don't need to send them all the paperwork, just have it kept on file if you are asked to produce your financial accounts etc.
Your actual turnover & profit/loss is irrelevant to the taxman as long as it doesn't ring any alarm bells, e.g. you turned over £20,000 but your expenditure was £1,000,000.
If you can't prove it, it didn't happen. That goes both ways too, remember