Business days vs. Your travel days count as business days, as do weekends and holidays if they fall between days devoted to business, and it would be impractical to return home. Standby days (days when your physical presence is required) also count as business days, even if you aren't called upon to work those days.

In the context of corporate travel and IRS tax deductions in 2026, travel days are officially treated as business days. If you spend a day traveling to or returning from a business destination via a reasonably direct route, that entire day is counted as a business day, regardless of how much actual "work" you perform. This is a critical distinction for the "Primary Purpose" test; if more than half of your trip consists of business days (including travel days, weekends "sandwiched" between work days, and actual meeting days), the cost of your transportation (like flights) is generally tax-deductible. However, in a general "office" context, "business days" usually refers only to Monday through Friday. If a company says a project will take "five business days," they mean five working days, and the time you spend on a plane on Sunday usually wouldn't count toward that project's timeline unless specifically designated as billable travel time.