You can help a taxpayer reconstruct their mileage records by using: Last year's mileage, plus the percentage of increase which their gross receipts increased over the prior year. A standard amount of yearly mileage for their type of business, available through IRS resources. The mileage information from their last year's tax return, because they said that their income and expenses were the same. An online map tool and their appointment book, receipts, or calendar records.