One client had moved several times and lost their records proving expenses. The IRS wanted $14k in additional taxes for three years because of no records. Two other CPA firms told him to pay the tax because he had no receipts and no records to prove deductions. We had him reconstruct his business trips and amounts spent based on the fact that his yearly sales calls and clients were usually the same. We had him make up expense reports by the month for three years detailing estimated amounts spent and mileage. IRS allowed all but $5k.
Tax settlement: $1,000 vs $14,000.