My first bit of advice would be everything - at least initially.
Secondly - back it up if practically possible or save it somewhere secure.
Can you go wrong if you save everything? Personally I think not. Yes it may take a little longer to file things or go through them at the end of the year, but whether you are attempting to complete your tax return on your own or have the help of an accountant or tax adviser, the full picture means it is far easier to remember things at year end and ensure you include everything.
Personally I would rather have too much than be left with unanswered questions. From this complete picture comes better advice. The same applies if you should be subject to an enquiry from HMRC, what may be irrelevant or insignificant to you may be useful in that instance.
So as a minimum think about the following:
You must keep a list or record of ALL your business income, that includes cash, cheques, payments directly to the bank etc.
Keep all of your receipts, even emails, in relation to expenditure you incur. Don't forget the stationery you slip into the weekly shop at the supermarket - it's business keep that receipt!
Keep bank statements and notifications of interest. This also includes for personal accounts too - you will need the year end interest statement for your self assessment tax return.
Note down where you go for meetings in relation to the business (think postcodes), when you have to pick up or buy business supplies (that may be business travel too).
Keep all correspondence, from customers, from suppliers, from HMRC and the Bank. All helps complete that full picture of your business, it is not always all about the numbers.
Not all accountants will have the same advice on record keeping and will offer a checklist of what is legally required. For KFH Accounts though, the better we understand your business the better the advice we can give on record keeping, cost savings and tax savings. With experience and advice you will learn what you really don't need to keep, but to start with find yourself a box and keep everything.
However you record all the above has to fit in with you and your business. When it becomes a chore you can miss things and it may be time to consider some help, that's where we come in. We can advise on systems and help you set them up or help you keep them updated.
The best advice I can provide is keep it simple, keep it detailed and update it regularly.
If you are not sure where to start then give us a call and we can help point you in the right direction are just put your mind at rest 0800 978 8241