If an audit becomes final including having exhausted all “official” channels of appeal; and the taxpayer failed to provide documentation supporting to either lower an assessment of tax liability or eliminate an assessment of tax liability (i.e. by providing proof of deductions or substantiating non-income deposits), the taxpayer may still have options.  In many cases, especially when the taxpayer was not at fault for not providing documents, the taxpayer may file an Offer in Compromise (“OIC”); Doubt as to Liability which in effect allows for an audit reconsideration.  If the appeals period is still open but is getting nowhere with the Revenue Agent or appeals officer, the taxpayer may file a petition in US tax court.  In your particular example, the fact that the tax preparer representing the taxpayer died during the audit should support the taxpayer’s claim of inability to submit documents and make the process of reopening the audit via an OIC easier.  If they documentation is unavailable the taxpayer should use secondary documentation such as bank statements and credit card statements to support their defense.  In addition a spreadsheet should be provided to summarize the various expense accounts.