Why Verbal Approvals Kill Your Margin

You're three months into an engagement. The client sends a Slack message: "Hey, can you guys also handle the data migration? Shouldn't take long."

Your PM says sure. The team spends six weeks on it.

Nobody documented it. Nobody signed anything. And when the invoice comes, the client pushes back — because as far as they're concerned, data migration was always part of the deal.

That's a verbal approval. And it happens all the time.

The Anatomy of a Verbal Approval

Statement of Work (SOW) reviews consistently surface one clause pattern that enables this problem more than any other: change control language that requires written approval but doesn't define what "written" means.

Your SOW probably says something like:

"Any changes to the scope of services must be approved in writing by both parties prior to implementation."

That sounds airtight. It isn't.

When your PM says "sure" in a Slack message, is that in writing? Technically, yes. Is it a valid change authorization under your SOW? Almost certainly not — but the client will argue it is, and you'll spend three hours in a tense call trying to explain the difference between a chat message and a signed Change Order (CO).

But the legal exposure runs deeper than most teams realize. In many states, oral contracts are legally enforceable if the standard elements can be proven: offer, acceptance, and consideration. That Slack message your PM sent? A client's attorney can argue it meets all three. You didn't just absorb undocumented scope — you may have created a binding obligation with no price attached.

Meanwhile, the work is already done.