In relation to expenses, if you are outside IR35, the revenue will allow you to claim back anything that is “wholly and exclusively necessary” to carry out the day to day running of your business.
HMRC have produced a comprehensive 100 page downloadable pdf called: ‘2007 Expenses and benefits - A tax guide’.
Remember you cannot claim for something you didn’t actually pay for in the first place, or can’t provide evidence that you did.
You will be personally liable for any underpaid taxes NOT the company you’re working through or taking advice from.
You should therefore steer clear of companies and scheme providers promoting generous expense allowances with ‘NO’ receipts required.