Get in touch with the Taxman before the visit. It’s perfectly acceptable to ask the Taxman why he wants to inspect your records he will usually tell you. This might allay some of your worries and allow you to focus on what he would like to inspect. Review the previous four tax years’ returns. If you find errors, notify him before the inspection starts. This will help to reduce any penalties he charges on underpaid tax. Be courteous as well because this helps the visit to go smoothly.