Bus factor, explained for business owners

Where the term comes from

Software teams coined it: how many people could get hit by a bus before the project is dead? The morbid framing stuck because the number is usually embarrassing. It applies to any organization where work depends on specific people, which is every small business.

Bus factor one in a twelve-person firm

In a firm that size, the controller often has a bus factor of one on eight or more processes: bank reconciliation, month-end close, card reconciliation, fixed-expense review, financial reporting to a franchisor or lender. Nobody else has ever done them. The org chart shows an accounting department of three; the reality is one person and two helpers.

How to count it

For each thing that matters, count the distinct people who actually touch it. Not who is allowed to. Who does. A shared mailbox with one sender has a bus factor of one regardless of how many people have access. A portal with one login has a bus factor of one regardless of who knows the password.

Directory and activity metadata in Microsoft 365 give you this count without reading anyone's messages.

What a two buys you

Going from one to two is the whole game. Two means a vacation is a vacation, a resignation is a two-week handover, and an insurer's continuity question has a real answer. Three is nice. Two is the target.