Every agency has the client they tell stories about. The one who asked for "just a small change" forty times. The one whose brother-in-law had opinions about the logo. The one who wanted the whole homepage redone the week before launch.
It is a comforting story, because it puts the problem outside the building. It is also mostly wrong. Scope creep is what happens when a boundary exists only in your head.
The client cannot see the line you drew
You know that "make the hero bigger" is ten minutes and "add a booking system" is three weeks. The client does not. From the outside both are one sentence in an email, and you have said yes to sentences before.
The first yes to an unscoped request is the one that costs you. It establishes that requests outside the agreement get done, at no cost, on request. Everything after that is the client behaving reasonably given the rules you taught them.
Write down what is out, not just what is in
Most proposals list what is included. Almost none list what is excluded, which is where every argument actually happens. Content writing. Photography. Stock licences. Third-party integrations. Post-launch changes. Training. Hosting migration from the old provider.
An explicit exclusions list is not defensive; it is the single cheapest thing you can add to a proposal. It converts a future argument into a present conversation, at a point where the client is still deciding whether to hire you rather than wondering why you are being awkward.
The sentence that handles it
When a request arrives that falls outside the agreement, the answer is never no. It is:
Happy to do that. It is outside what we scoped, so it would be an extra half day — want me to add it, or park it for phase two?
This works because it is not a refusal. It gives them the thing they asked for, priced, with a way to decline that is not embarrassing. Most clients park it. Some pay. Either outcome is better than doing it for free and resenting them.
The word "park" is doing real work in that sentence. "No" ends a conversation; "phase two" keeps the relationship and the revenue open.
Count revisions in rounds, not changes
Counting individual changes turns every project into an argument about arithmetic. Counting rounds — two rounds of consolidated feedback, say — turns it into a rhythm the client can follow.
It also fixes the drip. A client who knows they get two rounds gathers their thoughts and sends one considered list. A client with no limit sends whatever occurs to them at eleven at night, and each one costs you a context switch worth far more than the change itself.
When to just do it for free
Sometimes you should. If it takes five minutes, if it is genuinely your mistake, or if the relationship is worth more than the half day — do it, do not mention the cost, and bank the goodwill.
The distinction that matters is whether it is a decision or a reflex. Choosing to absorb something is generous. Absorbing everything because you never built a way to say otherwise is just an unpaid job with extra steps.