There is no 100% correct answer to this question. However, there are a lot of good-to-go answers that will fit almost every employer. The answers which are socially acceptable.
To discover what is expected from candidate to say, I want to dig into details why this questions is asked and what is show to employer.
Usually, this question is asked to determine which conditions made you uncomfortable and to compare them with the conditions your potential employer offers you. It's the best to answer really honest, but it's also desirable to spend less time on emphasizing the bad parts of your last job (the things you didn't like). It's much better to point out something positive like what you are looking for in the new job. By having this question answered, you let interviewer know whether it's possible for you and the company to have a match between your motives and their circumstances.
Also, an answer to this question can help employer to figure out a few important things:
- What can possibly demotivate candidate
- How candidate behaves in uncomfortable situations
- Which strategies candidate uses to solve such problems
- How candidate thinks of his (ex-)employer
The less desirable answer is something like "I had a conflict with management/team". Even if you didn't initiate this conflict, such answer makes not the best impression of you. Also, usually, it's not the best idea to mention material compensation as the main and only reason why you quit your last job. However, if you call such a reason you must prove that you are worth these money.
It shows what made you quit.
Reasons for that are always specific for each person, but the most common ones you can mention:
- Legacy project
- Tech stack of the project
- Culture fit
- Tempo of team
- Business processes weren't okay for you
- Lack of people to learn from
- etc etc etc
- not loyal customer
- etc etc etc