If you are investigated these are the things that HMRC will want to look at in detail

HMRC will have an estimate of what they think a dentist should earn and what their costs should be. It is up to you to prove your figures are right and you do this by having good records

HMRC have an elearning course outlining how records should be kept and what expenses are allowable, if you are investigated the first think you should do is check your records are correct before HMRC start to look through them. Read the elearning course here.