These two questions should be answered together.
I recommend that you discuss both points with the client and invite the manager of the person who raised the request.
During the meeting, I let the client explain why they need the change. In the beginning I might even respond with: We currently have no resources, but we’ll see how we can fit it in.
When do you need it by?
Can it wait after? [SOME IMPORTANT MILESTONE]
Naturally, the client will respond with "We need it as soon as possible! We can’t do our job without it!"
It’s not always true, but it’s the kind of bargaining that you should expect in such situations. It’s OK to challenge your client a little, but stay levelheaded and equitable.
You might find the following scripts helpful to qualify changes:
* If this item was so important, why was it forgotten in the first place?
* How often do you use/perform this process? (which requires the change)
* How would it affect your business if the [CHANGE] was not implemented?
* Is the change supported by your management?
After some discussion the client might even drop their requirement, because it’s actually not needed or you can agree on a later implementation date.
Whatever the outcome is, in the end the client will have to accept the extra budget for the change.