Stamp duty, it is a serious drag on people’s ability & willingness to move when they want to, whether that is for work, retirement, because they want to try a new area.
It's horrendously unfair. Elderly people can't downsize and free up large family homes for those who need them, as well as the pure nastiness of people who become disabled being taxed for their disability, if they have to move to a bungalow - which will likely be smaller than the house that they had no alternative but to leave.
It's also heavily skewed to benefit well-off people, who can afford to buy their 'forever home' immediately, rather than having to slog and save up and move up the property ladder gradually.
If we MUST have stamp duty, then after your first home, it should only ever be payable on the difference of the value of the more expensive home that you move to compared to the one that you leave. It's grossly unfair to charge somebody a tax for moving to an equivalent-value - or even lower-value - home for whatever reasons. This is for first/only homes, of course; if you can afford a second home, it's fair enough to pay a hefty tax on it.