Scope creep does not happen all at once. It comes about step by step, through small additions to which nobody would object.
The typical start: a small addition
The sentence "let us add this annex as well" is reasonable on its own. When it is repeated three or four times, the volume rises markedly above the estimate made at the outset.
The second source: formatting work
Rearranging tables, processing the text inside images or typesetting the document afresh may not be counted within the scope of translation. When this is not written down, it is expected to be done.
The third source: requests for extra rounds
When the number of correction rounds is not limited, the process does not close. Every round can generate new preferences.
The fourth source: preferences that arrive afterwards
Style preferences passed on after delivery are not a correction but a new piece of work. When the distinction is not drawn, the two look as though they were the same job.
Scope creep is hard on both sides
On the supplier's side the plan breaks down; on the buyer's side delivery is delayed. Nobody is acting in bad faith, but the outcome is negative for both sides.
The scope must be in writing
Which files, which sections, which formatting work and how many correction rounds. Four items prevent most scope creep.
Recording the change is enough
The aim is not to turn down additional requests. It is enough that the effect of each addition on the turnaround and on the scope is visible.
Counter-view: this much rigidity makes the work harder
Running a formal change process for every small addition looks disproportionate, and the objection is justified. The solution is simple: a defined tolerance for small additions, and a short notice for anything above it. What is needed is not rigidity but visibility.
Silent acceptance is the worst
Doing additional work silently looks like goodwill in the short term. In the long term the expectation shifts, and a problem arises on the day it cannot be done.
The volume is measured again
When an addition arrives, the word count is repeated. An assessment of "a small addition" made by eye is wrong more often than not.
The schedule is updated as well
If the date stays fixed while the scope grows, the squeeze is loaded directly onto the review step.
Who will approve is written down
If it is undefined who may accept a change of scope, each addition comes from a different person and nobody sees the total.
Scope creep can be measured
Comparing the volume at the start with the volume at delivery shows how often scope creep occurs.
Recurring scope creep is a sign about the process
If the scope grows on every job, the problem lies not in the requests but in the job being incompletely defined from the start.
Scope creep more often than not starts in good faith
The supplier does the small additions without questioning them in order to protect the relationship, and the buyer thinks this is normal. In a process where both sides act in good faith, the scope drifts to a point on which nobody made a decision, and once it is noticed it becomes hard to bring back.
Takeaway
Scope creep is born not of bad faith but of a start that was not put in writing. When the list of files, the boundaries of the sections, the formatting work and the number of rounds are written down at the outset, additional requests cease to be a problem; they simply become visible and the decision on them is made jointly.