Whose mistake was it or Whose fault was it?

Question

I understand that we should use "It's your fault" and not "It's your mistake". However, I have heard this question: "Whose mistake is it". Is this wrong or is this acceptable?

Answer 1

The two terms have different connotations. "Fault" almost always involves guilt. It's your fault, so what do you intend to do to make it right again? What will your penance, your atonement be?

On the other hand, a "mistake" can be (doesn't have to be, but can) less connected with guilt. There's even the phrase "a honest mistake", describing something anybody could have been wrong about. Merriam-Webster gives the example

Don't worry about it. It was an honest mistake.

So, whether "Whose fault is it?" or "Whose mistake is it?" fits better, will probably depend on how much guilt you'd like to imply.

As a side note, because the action probably is in the past, "Whose mistake was this?" or "Who did this mistake?" would sound more natural.