[Jakob]

Most countries have mandatory tax withholding by the employer, but not all (e.g. Singapore, Indonesia). In that case you would pay the taxes yourself.

What I haven’t heard yet, is not being allowed to sell on the settlement date. That puts you in a serious risk:

Worst case, the stocks fall to zero, but you paid taxes from your private money. This is net-negative.

To avoid that risk, either the employer needs to withhold the taxes or needs to allow you to sell the tax amount on the first day.