The best way to prove business travel expenses (including hotels, flights, rental cars, meals, and entertainment) is to use a credit card slip (using your business card, of course) with additional notes on the business purpose. Make the note at the time you incur the expense.

Proving a business trip for tax or reimbursement purposes requires a rigorous "paper trail" that establishes the business necessity of the travel. The IRS and most corporate accounting departments require a "contemporaneous record," meaning you should document the trip as it happens rather than months later. Key evidence includes an official itinerary detailing meeting times, locations, and the names of the individuals or companies you visited. You should save all original receipts for lodging, airfare, and transportation, but more importantly, you need to document the "business purpose" for each expense—for example, a meal receipt should have the names of the clients present and the specific project discussed written on the back. Supporting evidence like meeting agendas, email threads confirming appointments, or conference registration badges are vital. In 2026, many professionals use apps like Expensify or SAP Concur to scan receipts and GPS-log their mileage in real-time. If the trip includes personal "bleisure" days, you must clearly segregate those costs and only claim the portions that would have been incurred solely for the business part of the journey to avoid an audit.