If you own your own company or are self-employed then you should already be aware of the records you need to keep. These records often need to be kept for a minimum of five years and should be stored in a secure location and ideally backed up.
The best way to keep accurate and sufficient records is to make sure you have good systems in place to start with. Prior to starting trading or within the first week, you should ensure that you have spreadsheets set up for all of your costs and income etc. If you are using software to do this, then make sure that it is set up and that you are fully aware of how to use it. Records can often be back dated but this can make a simple job long winded and also can mean that you forget or miss things. It also means that you do not have a true view on how your business is progressing and if you are making a decent profit.