answer:I don’t think there’s anything unethical about quoting extra for unforeseen problems, as long as you don’t stick to the “top of the range” if those unforeseen problems do not occur. In other words, are you being honest? If so, then your precaution is very sensible, and your client should appreciate it. But from their point of view, it likely makes sense to make you aware that they expect you not to “pad” the invoice. Did you explain again what you had originally meant, and how did they react to that?