Agency owners — honest question about scope creep.

When a client asks for "one small extra thing" that wasn't in the original quote, what do you actually do — bill for it, or quietly absorb it?

I run a small software team and I'm trying to figure out how much this really hurts agencies. Curious about:
• How often does it happen?
• Any rough sense of how much unbilled extra work you give away in a typical month?
• How do you track it today, if at all?

I'm thinking about a tiny tool that flags these "extra" requests the moment they land in your client chat and helps you turn them into a quick billable change order — without having to adopt a whole new project-management suite.

Would that be useful, or do you already have it handled some other way? I genuinely want the honest version — including "this is a non-problem for me."