For this year, you shouldn’t be taxed at the 20% rate. Instead, you should be taxed at the same rate as Taiwanese people. At all the schools that have hired me, if I start working before July 1st, then they withhold taxes at the same rate as for Taiwanese people, which comes to less than 10% after the standard deduction and personal exemption.
On the other hand, if I start working afterJuly 1st, then they look at my passport to see how many days I’ve already been in the country that year. If it’s already at least 183 days, then they still fill out the tax form so that I’m taxed at the same rate as a Taiwanese person.
But if it’s after July 1st and my passport shows that by December 31st that year, I will have been in Taiwan less than 183 days, then the school fills out the form so that I’m taxed at the flat 20% rate only for the rest of that year. Then in December, I notify the school (in case they forgot) that starting January 1st, they have to withhold taxes from my salary at the same rate as a Taiwanese person. And they have always agree to do this for me.
However, I have a friend who had a different experience. For him, the school refused to change the withholding amount on January 1st, claiming that he might quit before June 30th, in which case he would be liable to be taxed at the flat 20% rate. He kept trying to argue with them, but they kept refusing. So he had to put up with having a 20% chunk taken out of his salary for the next six months. Finally, on July 1st, since he had already been in Taiwan for 183 days that year, they agreed to change his withholding amount to be the same as Taiwanese people.
So then the next January, he went to the tax office and filled out the tax form (it’s a special form for foreigners) and it turned out that he was entitled to a huge refund. For Taiwanese people, they simply wire the refund to your bank account. But for foreigners, they refused to wire tax refunds. So they sent him a notice in the mail in April, and then he had to go to the tax office in person to pick up his refund, which was in cash.