What you need to know to ensure your allowable business, charitable and medical miles are not dismissed during an audit. The tax code allows deductions for qualified miles driven for business, medical, moving and charitable purposes. But to claim this deduction you must keep adequate records of actual miles driven. During an audit this is an often disallowed deduction, despite the fact that you actually drove the distance claimed. How to make sure this doesn’t happen to you? Here are some tips. Keep a log. The tax code is clear on this point. You may not estimate your miles driven.