The responsibility to prove entries, deductions, and statements made on your tax returns is known as the burden of proof. You should keep adequate records to prove your expenses or have sufficient evidence that will support your own statement. You generally must have documentary evidence, such as receipts, canceled checks, or bills, to support your expenses.
Additional evidence is required for travel, entertainment, gifts, and auto expenses.
The Restructuring and Reform Act of 1998 calls for a shift in the burden of proof to the IRS in a court proceeding. This shift to the IRS to prove an item on your tax return occurs only in a court proceeding and only if you have met your recordkeeping requirements.