How do you push back on scope creep… without damaging the relationship?

I believe everyone is familiar with this scenario… a customer who is constantly adding “small” requests.

Most of the time, we just do them because they’re small and it’s not worth arguing or risking the relationship.

But over time, this leads to delays in already committed work and team frustration (rework and changes that were never discussed upfront). At the same time, the budget starts bleeding.

I know the real problem here is that we don’t have a detailed written product description. It’s not like we have nothing—of course, the customer received a quote with a description of the features to be delivered—but sometimes the edges are blurry, and different implementation approaches can lead to significant scope creep.

My approach: if a customer asks for something that I believe is out of scope, I tell them I need to discuss it internally with the team. Then I explain what we consider to be in scope and how much additional effort their request would require.

Sometimes this works well, but when it happens frequently, I can see that they start getting frustrated.

I’m wondering- what is your approach in situations like this?