Have you ever underquoted a job? What happened?

Anybody who has done this for years and says no is either new or not being straight with you. It happens on projects where something surfaces that could not be seen from outside: undocumented cabling, a system that turns out to be load bearing, a vendor dependency nobody mentioned.

Our rule is simple. If we misjudged the scope, that is ours to eat. If the scope genuinely changed or we found something new, we stop, tell you what we found, and give you a revised number before continuing. You do not get a surprise on the final invoice.

Ask any provider this question. How a company handles being wrong is something you will eventually need to know, and it is better to hear the answer before you hire them.